Objective To research the effect of trolamine complexing agent on structure and properties of electroless Ni-W-P alloy coating. Methods Ni-W-P alloy coating was prepared on 40Cr substrate by chemical plating. The effect of trolamine on structural components, deposition rates, corrosion resistance and porosity of Ni-W-P alloy coating was investigated. Results When concentration of trolamine was 8 mL/L, the mass fraction of coating W and P reached at the peak 3.63% and 9.34% respectively. The coating was amorphous structure when concentration of trolamine concentration was low while it began to take on cystalline state peak and have mixed cystalline when the concentration reached 12 mL/L. Trolamine concentration had great influence on the deposition rate and porosity of the coating. The deposition rate reached maximum 14.1 μm/h as the trolamine concentration increased, and the coating porosity reached minimum 0.07% when the trolamine concentration decreased to 8 mL/L. The corrosion resistance of the Ni-W-P alloy coating tended to firstly increase and then fall down with the increasing trolamine concentration in plating bath. The Ni-W-P alloy coating had the best corrosion resistance at corrosion rate of 5.6 μm/a and concentration of 8 mL/L. Conclusion The use of trolamine as complexing agent can produce Ni-W-P alloy with uniform and fine cellular particles and has a certain influence on the structure of the coating. It can improve the deposition rate of the Ni-W-P alloy coating. The Ni-W-P alloy coating has good corrosion resistance with the minimum corrosion rate at 5.6 μm/a.