Aiming at the machining difficulty and low machining efficiency of titanium alloy, the influence of milling parameters of aviation TC18 titanium alloy on surface roughness, machined surface morphology and metallographic structure was analyzed in order to improve the quality of machined surface. Two prediction models（exponential model and multiple quadratic regression model） were established by using taguchi and optimization module design methods, and multi-objective genetic algorithm and response surface method were respectively used for parameter optimization aiming at improving surface quality and machining efficiency.The results show that: The order of influence of each parameter on the surface roughness is feed f,>,milling depth a,p,>,milling width a,e,>,speed of mainshaft n; The multiple quadratic regression model has higher significance and the surface topography obtained from the combination of response surface optimization parameters is optimal. The microstructure of the milling section of TC18 titanium alloy was observed.The results showed that the equiaxed α phase near the machined surface was elongated and strip secondary phase were precipitated.