O-alkyl etbylphosphonodithionio acids were prepared by the reaction of ethylthionophosphine salfide dimer(C₂H₅PS₂)₂ with alcohols.Eighteen N-sobstituted O-alkyl-S-(oarbamoylmethyl) phosphonodithioates were prepared by method A or B.In method A,the O-alkyl-S-(carbamoylmethyl) ethylphosphonodithionic acid is not isolated.In method B,the intermediate aoid is isolated and purified.Then the aoid in the presence of sodium carbonate and acetone reacted with N-substituted a-ohloroacetamide to give the title compounds.The yield is over 60%.The structural formula,melting points,boiling points,elemental analyses of these compounds were listed in the Chinese text.