The invention discloses a formula and a preparation method of a detergent for a circuit board of a computer. The formula contains alcohol, a glycol derivative, an onionic surfactant, N-alkyl pyrrolidone, coconut oil diethanolamide, polymethylsiloxane, dodecyl dimethylamine oxide, solvent propylene glycol butyl ether, bromopropane and butanediol. Compared with the prior art, the detergent is non-conductive and volatile liquid with a cleaning effect after being mixed, the circuit board of the computer is brushed through the cooperation with a hairbrush and is naturally air-dried, and an antioxidant insulation layer is remained after the air-drying, so that the circuit board of the computer can be further protected, and the use performance of the computer is improved; and the detergent has popularization and application values.