The invention relates to a method of a part thermal spraying coating, in particular to a method for a high velocity oxy-fuel coating on the bottom face of a shielding groove-shaped part. In order to solve the problem that continuous spraying of the bottom face of the shielding groove-shaped part is difficult, a left and right two-section subsection high velocity oxy-fuel manner is adopted, and the step-by-step distance and the spraying angle are accurately controlled to form the coating with the good thickness uniformity on the bottom face of the shielding groove-shaped part; the internal distance between left and right two spraying sections is accurately controlled, good lap joint between the left and right two spraying sections is achieved, and preparation of the uniform and continuous coating of the shielding groove-shaped part is achieved. According to the method, implementation is easy and convenient, the problem that spraying on the bottom face of the shielding groove-shaped part is difficult is effectively solved, the prepared coating has the excellent thickness uniformity and surface continuity, and the operating characteristic and requirement of spraying zones of the shielding groove-shaped part are effectively met.