abstract: In this talk, I will present our team’s recent works on KAM theory. (1) It is proved that there are many infinitely dimensional KAM tori of prescribed Diophantine frequency for a class of infinite dimensional lattice system of short range. (2) We give out a criterion to decide whether or not there are KAM tori of finite dimension for a degenerate Hamiltonian system of infinite dimension. (3) It is shown that there are many KAM tori for Pochhammer-Chree equation where the normal frequencies have a finite limit.