Some problems still exist in 3D garment modeling and simulation, including that the model is complex, the efficiency is low, and the structural characteristics of garment are ignored. An improved spring-mass model is proposed, by which 2D→3D transformation and simulation of garment are formulated unifiedly. The dynamic system of modeling and simulation is derived and solved using time differentiate method, with given composition and expression of internal and external cloth forces in the formulation. And then the simulation algorithm is described. Overcoming the serious weakness representing cloth properties simply of previous model, the improved mass-spring model considers mechanical properties of cloth such as stretching, shearing and bending. Structural characteristics of garment such as dart and pleat are took into account too, thus complex garment pattern can be modeled and simulated. Compared the efficiency and the effect of simulation with other simulation systems, the resulting simulation system is faster and more realistic. The technique has been used in some garment enterprises and gets well responses.