Abstract: As starting material, Na salt of -O,O--dialkyl dithiophosphoric acid reacts with alkyl halide to give -O,O--dialkyl -S--alkyl(allyl) dithiophosphate, which is dealkylated with dimethylamine forming -O--alkyl -S--alkyl(allyl) ammonium dithiophosphate, then it is treated with phosphorus pentachloride or phosphorus oxychloride. The chlorination product, dithiophosphorochloridate, further reacts with a substituted phenol in the presence of a base to give -O--alkyl -S--alkyl(allyl) -O--substituted phenyl dithiophosphate. By the above method, twenty-eight new title compounds were prepared. The bioassay results against plant disease fungus including, -B. cinerea, R. solani, Hypochuns sasakii- Shirai,- A. solani, P. zeae, P. piricola, C. arachidicada and P. oryzae- show that the title compounds towards the -P. oryzae- fungi possess a satisfactory or excellent fungicidal activity at 0.005% concentration -in vitro-, but they have non- or only lower fungicidal activity towards other seven plant disease fungus.