吹毛求疵

chuī máo qiú cī

to nitpick

Character by character

吹chuī
blow

毛máo
fur

求qiú
seek

疵cī
flaw

老板总是吹毛求疵，连标点都要改。

The boss is always nitpicking; he even corrects the punctuation.

Tone: negative (criticism).

Blowing fur apart to find a flaw in the skin. Everyday version: 鸡蛋里挑骨头.

Learn it in context

This idiom and thousands more are in Learn Chinese with Bao, with audio, pinyin and drills that make them stick.