The invention provides an electric deposition preparation method of a Ni-Co-B alloy substituted hard chromium plating, relating to a preparation method of the Ni-Co-B alloy substituted hard chromium plating. The method 1 comprises the following steps of: taking nickel salt, cobalt salt, nickel chloride, boric acid, amine boride, NI3<#> fast high-level nickel-plating glazing agent A and lauryl sodium sulfate; preparing an alloy plating solution; and plating a processed plated part. The method 2 comprises the following steps of: taking nickel chloride, cobalt salt, boric acid, amine boride, NI3<#> fast high-level nickel-plating glazing agent A and lauryl sodium sulfate; preparing an alloy plating solution; and plating a processed plated part. In the invention, a Ni-Co-B alloy plating with uniform brightness, hardness of 770-800HV50 as well as good corrosion resistance and bonding force is obtained at a deposition rate higher than 60mu m/h. In the plating process, the cathode current efficiency is higher than 96%; and after the plating is subjected to heat treatment at 150-400 DEG C for 1-3 hours, the hardness of the plating can be increased to 1055-1108HV50.