This invention relates to a method be able to carry out perfect forecast to diesel engine particulate filter acoustic characteristic. The invention uses two temperature probe and two pressure gauge separately to measure parameter of diesel engine exhaust condition; utilize Sysnoise acoustic analysis software to carry out thermal state triaxiality numerical simulation count to reduced particulate filter model, and by result to get particulate filter's transfer matrices; take into account of air flowing viscosity effect in particulate filter, to carry out viscous correction to original transfer matrices, gain particulate filter transfer matrices of viscous corrected; at last adopt transfer matrix method to count particulate filter insertion loss on thermal state. This method is able to apply at more widely frequency band. It overcomes shortcome of narrow forecast frequency band of one dimension analytical method. It can carry out more precise forecast to acoustic characteristic of exhaust air system.