Fifty-five compounds of s-tetrazine derivative including hexahydro-, 1, 6-dihydro, 1, 4- dihydro-, 1, 2-dihydro-and aromatic s-tetrazine were prepared. Their antitumor activities were evaluated in vitro by MTT method for P-388 cell and SRB method for A-549 cell. The results show that there are 9 compounds which in 10− 6 μM have more than 50% inhibition rate to A-549 cancer cell growth, and 7 compounds in 10− 6 μM have more than 50% ...