To prove Yau's Uniformization Conjecture, Wan-Xiong Shi
initiated studying the Ricci flow on complete noncompact Riemannian
manifolds. The first important thing in the study of the Ricci flow on
Riemannian manifolds which we have to consider is the short-time
existence of the solution. In this talk, using Deane Yang's local Ricci
flow, we prove the short-time existence of the Ricci flow on noncompact
manifolds, whose Ricci curvature has global lower bound and sectional
curvature has only local average integral bound. As a corollary of our
main theorem, we get the short-time existence part of Shi's theorem in
this more general context.