In order to solve the problem in simulating of the complicated organization of weft knitted fabric and lack sense of reality,mass-spring model was improved and threedimensional mass-spring model was proposed.The complicated organization of weft-knitted fabric could be well simulated via the improved mass-spring model.The phenomenon of super-elastic in fabric dynamic simulation was also solved by non-linear spring force.The spatial displacement of particles was calculated using velocity-Verlet numerical integration to realize the 3D dynamic simulation of weft knitted fabric.The algorithm showed its advantages on computing speed and real-time performance.