I am trying to divide 2 histograms by using

TH1F *a = (TH1F*)h1->Clone();

a->SetTitle(“h1/h2”);

a->Divide(h2);

a->Draw();

but the result I got is almost flat, how can I change the distribution ?

Your histograms are very similar. So you get 1. . That’s correct.

( x/x = 1 if x not equal to 0)