1、用法不同

on account of 语气较为正式。可作状语、表语, 不作定语

例句：He could not come on account of his illness．

他因病不能前来。

account for 对…负有责任；对…做出解释；说明……的原因

例句：He could not account for his absence from school.

他无法说明他旷课的原因。

2、含义不同

on account of 因为...由于...为了...的缘故

例句：That was on account of lack of exercise．

那是由于缺乏锻炼。

account for 对...说明...的原因

例句：Computers account for 5% of the country's commercial electricity consumption. 计算机占去该国商业用电的5%。

拓展：

关于account的实用短语：

account可以表示“账户”

(1) bank account “银行账户”

(2) open a bank account “开一个银行账户”

(3) close a bank account “注销一个银行账户”

(4) savings account “储蓄账户”

(5) deposit account “存款账户”

(6) checking account “活期存款账户，支票存款账户”，美式英语

(7) current account “活期存款账户”，英式英语

(8) joint account “联名账户”。