To solve the problems of traditional high temperature electroless nickel plating process, the effect law of lactic acid, glacial acetic acid and composite complexing agent on electroless Ni-P plating on brass surface was studied by using nickel sulfate as main salt, sodium hypophosphite as reducing agent and sodium acetate as buffer agent in acidic nickel plating system at medium temperature(70 益 ) . The results show that, in the composite complexing agent, actic acid mainly plays the role of complexing agent, where as glacial acetic acid mainly plays the role of buffer. Meanwhile,compared with single complexing agent,composite complexing agent has the same deposition rate, but its bath stability and porosity of plating is better. A bright , smooth plating with dense appearance and combined well with the brass surface could be obtained with actic acid of 7 . 5 mL / L and glacial acetic acid of 13 mL / L. The hardness of coating can reach 515 HV and the porosity is lower than 1 cm^-2, which exhibits coating had good abrasion resistance and corrosion resistance.