NEW MATERIAL:A compound expressed by formula I (R1 and R2 are 1W4C alkyl; R3 is Cl, methyl, nitro or methylthio or as necessary phenyl which is substituted by nitrile, 1W4C alkyl or 5-methyl-2-isoxazolyl; X is O or S).

EXAMPLE: N-Ethyl-N-isopropoxycarbonyl-O-4-cyanophenylmethyl-phosphoamide thionate.

USE: An insecticide.

PREPARATION: For example, a carbamic ester derivative expressed by formula II is reacted with methylphosphonothioic dichloride in the presence of triethyl amine in dioxane under reflux to provide a methylphosphonothioylchloride derivative expressed by formula III, which is then reacted with a compound expressed by the formula HX-R3 in the presence of triethylamine in THF at 0°C W room temperature.