The invention belongs to the technical field of diamond surface treatment and particularly relates to an electrocorrosion-preventing treatment method for the surface of nickel-plated diamond. The electrocorrosion-preventing treatment method includes the following steps that firstly, a treatment solution is prepared, wherein the solution with 10 g/L to 15 g/L of cobaltous sulfate and 5 g/L to 8 g/L of sodium fluosilicate are prepared, and the pH is adjusted to range from 2 to 4; secondly, a nickel-plated diamond particle is added in the treatment solution of the first step, water bath heating is performed till the temperature reach 60 DEG C to 75 DEG C, and the temperature is maintained; thirdly, a strong oxidant is added to the treatment solution and stirred for 8 min to 15 min, and a cobalt-containing electrocorrosion-preventing layer is formed on the surface of the nickel-plated diamond particle; and fourthly, the nickel-plated diamond particle obtained after treatment is obtained through precipitating, filtering and drying. The nickel-plated diamond particle treated through the above method has high electrocorrosion-preventing performance, meanwhile has certain electroplating activity and has good embedding performance and the long service life when applied in the production process of electroplated diamond wires.