The invention relates to a cooling fan blade of a diesel engine and a manufacture method thereof and belongs to the technical field of diesel engines. The cooling fan blade of the diesel engine comprises the following components in parts by weight: 70-90 parts of polypropylene, 15-20 parts of high-density polyethylene, 0.15-0.20 part of hydroisomerization dewax base oil 5CST, 0.13-0.18 part of hydroisomerization dewax base oil IOCST, 0.1-0.3 part of antioxidant CA (carbonic anhydrase), 0.5-1.0 part of ultraviolet absorbent and 0.1-0.3 part of dilauryl thiodipropionate; and the cooling fan blade is manufactured by virtue of extruding and injection molding. By using the manufacture process, the stress concentration factor is reduced, the impact resistance and fatigue resistance are improved, the flowing and mold-filling performance of the plastic melt is improved, the flowing resistance and local residual stress are reduced, the cracking and warping are prevented and the appearance of the cooling fan blade is beautiful, thus the cooling fan blade can be widely applied to medium trunks, especially to diesel engine trunks.