Abstract: In order to decrease the toxicity and enhance the curative effec tof niridazole against Schistosomiasis japonica, a series of acylates of niridazole has been prepared through acylation of niridazole with appropriate acid chlorides or anhydrides. The analogs of niridazole, 2-substituted acetamido-5-nitrothiazoles and 1- (5-nitro-2-thiazolyl) -4-acylpiperazinse were also prepared. The products has been tested against Schistosomiasis japonica in mice.Preliminary test results showed that the majority of aliphatic acylates of niridazole exhibited marked schistosomicidal effect against adult worms as well as larva (compounds 2, 4～8, 12, 13, 15, 18, 19),a few of aromatic and heterocyclic acylates (compounds 14, 22) and the analogs of niridazole (compounds 26, 39, 49) showed weak activity.