Add fuel to the fire 火上浇油

Also, add fuel to the flames. Worsen an already bad situation, as by increasing anger, hostility, or passion.This metaphor dates from Roman times--Livy used it in his history of Rome--and it remains in common use.

eg: Bill was upset, and your making fun of his mishap just added fuel to the fire.

Note:

Add fuel to the fire也可以说add fuel to the flames，意思是使本来很坏的情形更糟糕，例如让人更加生气、更加热情等。罗马历史学家李维曾用它描述罗马历史。

例：Bill很烦躁，你用他的事情打哈哈纯粹火上浇油。