The invention discloses a method for specifically detecting isocarbophos in a catalytically colorimetric mode through interaction of a random ssDNA sequence, Hemin and a target in a NaH2PO4 buffer solution. Reagents adopted for the method mainly comprise the random ssDNA sequence, Hemin, H2O2 and 3,3',5,'5-tetramethyl benzidine (TMB). When the random ssDNA sequence and Hemin are firstly incubated for a certain time, the random ssDNA sequence can cover the surface of Hemin, the activity of Hemin for catalytically oxidizing TMB is restrained temporarily, N atoms in substrate molecules lose one electron, the color of the system is remarkably changed into light blue or blue from colorless originally, and at the moment, characteristic absorption peaks of a product are 370 nm and 650 nm. If isocarbophos is added into the system to jointly act for a certain time, the catalytic activity of hemin is greatly enhanced, substrate TMB loses two electrons and is changed into a diimine structure, at the moment, the color of the system is changed into yellow from blue, the characteristic absorption peak exists at the position of 450 nm, and the change amplitude of the light absorption value at the position of 450 nm and the concentration of isocarbophos are in direct proportion.