There are several areas in which British and American spelling are different. The differences often come about because British English has tended to keep the spelling of words it has absorbed from other languages (e.g. French), while American English has adapted the spelling to reflect the way that the words actually sound when they're spoken.
英式英语和美式英语的拼写在某些地方不尽相同。原因是英式英语更倾向于保留外来语（如法语）的拼写，而美式英语的拼写反映了单词的实际发音。

If you're writing for British readers, you should only use British spellings. In one or two cases, the preferred American spellings are acceptable in British English as well, especially the -ize/-ization endings. While you can use both the -ise/-isation or the -ize/ization endings in British English, it's important to stick to one style or the other throughout the same piece of writing.
如果你的读者是英国人，那么就应该使用英式拼写。偶尔几种美式拼写也能被英式英语接受，特别是以-ize/-ization结尾的单词。英式英语中可以使用以-ise/-isation或-ize/ization结尾的单词，但重要的是在一篇文章内保持同一种拼写方式。

Here are the main ways in which British and American spelling are different.
以下是英式和美式拼写的主要不同。

Words ending in –re
以-re结尾的单词

British English words that end in -re often end in -er in American English:
英式英语中以-re结尾的单词通常在美式英语中以-er结尾。

British US
centre center
fibre fiber
litre liter
theatre theater or theatre

Words ending in –our
以-our结尾的单词

British English words ending in -our usually end in -or in American English:
英式英语中以-our结尾的单词通常在美式英语中以-or结尾。

British US
colour color
flavour flavor
humour humor
labour labor

Words ending in -ize or –ise
以ize或ise结尾的单词

Verbs in British English that can be spelled with either -ize or -ise at the end are always spelled with -ize at the end in American English:
英式英语中以-ize或-ise结尾的动词都是合乎拼写规则的。但在美式英语中，它们总是以-ize结尾。

British US
apologize or apologise apologize
organize or organise organize
recognize or recognise recognize

Words ending in –yse
以-yse结尾的单词

Verbs in British English that end in -yse are always spelled -yze in American English:
英式英语中以-yse结尾的单词在美式英语中总是以-yze结尾。

British US
analyse analyze
breathalyse breathalyze
paralyse paralyze

Words ending in a vowel plus l
以元音+l结尾的单词

In British spelling, verbs ending in a vowel plus l double the l when adding endings that begin with a vowel. In American English, the l is not doubled:
英式英语中，在以元音+l结尾的单词后面加上由元音开始的后缀时，l要重复1次。美式英语则没有这一要求。

British US
travel travel
travelled traveled
traveller traveler

Words spelled with double vowels
含有2个连在一起的元音字母的单词

British English words that are spelled with the double vowels ae or oe are just spelled with an e in American English:
英式英语中含有ae或oe的单词在美式英语中只写作e。

British US
leukaemia leukemia
manoeuvre maneuver
oestrogen estrogen

Note that in American English, certain terms, such as archaeology, keep the ae spelling as standard, although the spelling with just the e (i.e. archeology) is usually acceptable as well.
注意：美式英语中，一些专有名词如archaeology还是会保持标准的写法，虽然只写e(例如archeology)也不是不能接受。

Nouns ending with –ence
以-ence结尾的名词

Some nouns that end with -ence in British English are spelled -ense in American English:
英式英语中某些以-ence结尾的名词在美式英语中以-ense结尾。

British US
defence defense
licence license
offence offense

Nouns ending with –ogue
以-ogue结尾的名词

Some nouns that end with -ogue in British English end with either -og or –ogue in American English:
英式英语中某些以-ogue结尾的名词在美式英语中以-og或ogue结尾。

British US
analogue analog or analogue
catalogue catalog or catalogue
dialogue dialog or dialogue

The distinctions here are not hard and fast. The spelling analogue is acceptable but not very common in American English; catalog has become the US norm, but catalogue is not uncommon; dialogue is still preferred over dialog.
上面这条规则并非一成不变。Analogue可以接受但在美式英语中并不常见。Catalog已经成为美式标准，而catalogue也很常见。人们更愿意使用dialogue而非dialog。

Aside from spelling differences, many items and practices have different names in British and American English. To explore further, see British and American terms.
除了上述的拼写区别，英式英语和美式英语也有许多用词方面的不同。感兴趣的话戳这里吧：英国人不说的300个单词