Usage and Grammar of 看我这脑子
看我这脑子



看： see or look;
我： here means 我的，mine;
这： such;
脑子： head;


As a whole, "Look, (that is) such a head of mine!" or "See, (that is) such a head of mine!" It means I am not that intelligent or brainy. In this context, it is specifically referring to one of the functionalities of a head, memorizing things, and it's just like to say "oh, my bad memory" or "look, my bad memory".