The chemical Ni-P coating has been widely used in corrosion protection of marine engineering equipment due to its excellent corrosion resistance and wear resistance. However, when traditional chemical plating is adopted to prepare Ni-P coating for the B30 Cu-Ni alloy tubes, which are commonly used for marine equipment cooling systems, the quality of the Ni-P coating is easily affected by ion “depletion” and difficulty in removing bubbles inside the tube. Flowing chemical plating is expected to solve this problem. However, the flow velocity of the chemical plating solution may be the key factor affecting the performance of the resulting Ni-P coating, so it is of great significance to clarify the optimal flow velocity of the chemical plating solution for obtaining high-performance Ni-P coatings. Hence, the chemical plating Ni-P coating was plated on the inner wall surface of B30 Cu-Ni alloy tube via a home-made electroless plating set for tubes with by varying the flowing rates of a designed plating solution. Then, the acquired coatings were characterized by means of erosion-corrosion test, electrochemical tests and surface morphology analysis etc., in terms of the effect of the flowing rates of plating solution on the quality of the plated coatings The results show that the flowing rate of chemical plating solution affects the surface morphology, deposition rate, and erosion-corrosion resistance of the Ni-P coating, but has few effects on the composition, hardness, and crystal structure of the coating. Compared to the bare B30 Cu-Ni alloy, the Ni-P coatings obtained under different flow rates of the plating solution all demonstrate superior erosion-corrosion resistance, among others the coating prepared with the chemical plating solution with flowing rate of 1.6 L/min exhibits the highest resistance to erosion-corrosion.