This paper concentrates on search of powerful codes for TCM. We verify and modify the search procedure developed by Ungerboeck[1]. More sophisticated results are obtained. The results indicate that the best TCM codes with maximum free Euclidian Distance （ED） are more than one for a given constraint length and modulation scheme. The TCM codes with the simplest structure are listed in this paper. We also search the powerful TCM codes for minimal encoders

and find that in some cases the minimal encoders can reach the maximum free ED while the systematic encoders with the same parity-check polynomials can not.