Abstract: We implement a multigrid method on GPU and improve the accuracy of 2D realtime fluid simulation by using the implemented multigrid method.We use four layers of grids in our GPU based multigrid method,and by using frame buffer extension and the way of rendering to textures,we manage to put all the textures needed in graphic hardware memory to increases the rate of utilization of GPU.The test results show that our method can improve the accuracy of GPU based 2D rea-l time fluid simulation with the same fps.Especially in lager scale situation our method speeds up the simulation by times compared with other GPU based rea-l time fluid simulation using normal iteration method with equivalent accuracy.