这句汉译英对不对？

正确如下：
Sina Media, the short name for Sina Media Creative Agency.

be short for意思是：某某的缩写，请你仔细想想？

新浪传媒，全称为新浪传媒创意机构。

如果按你原句的字面翻则为：
Sina Media, the full name is called Sina Media Creative Agency

Sina Media is short for Sina Media Creative Agency.

同意LS，或者说，
Sina Media, whose full name is Sina Media Creative Agency.

错了哦.
你的意思刚好相反了.你说的是新浪传媒是新浪创意机构的全称了.