Abstract：According to General Relativity theory, light rays can be deflected when they propagate in our universe. The tidal gravitational files lead to differential deflection of light bundles and therefore change the shape 、flux and size of the distance objects. These are so-called gravitational lensing effects. In this talk, I will focus on the weak lensing effects which caused by the large-scale structures, introduce some basic theories and cosmological applications of weak lensing, our ray-tracing simulation results and the comparison with observations.