Ricci curvature lower bound play very important rule for geometric analysis on Riemannian manifold. So it is very interesting to introduce similar concept on discrete setting especially on graphs. We will talk about the Ricci curvature lower bound on graphs where the original idea comes from the Bochner formula on Riemannian geometry. Given some Ricci curvature lower bound on graphs, we will imply some classic results from Riemannian manifold for Li-Yau gradient estimate, Harnack inequality and heat kernel estimate, as well as the volume doubling property and  Poincare inequality on graphs.