The invention provides a carbon fiber composite foam core sandwich structure wind tunnel fan blade. The wind tunnel fan blade is characterized in that a skin is arranged at the outer part; the internal front end of the skin is connected to a front edge reinforcing area; the internal middle part of the skin is connected with a main bearing beam; an internal space defined by the skin, the front edge reinforcing area and the main bearing beam is filled with a foam core material; the skin comprises an inner skin and an outer skin; the outer skin is laid and adhered to the surface of the inner skin; the thickness of the main bearing beam is changed from 8-10 mm at the root part of the blade to 2-4 mm at the tip of the blade; the thickness of the front edge reinforcing area is 2-5 mm, the thickness of the inner skin is 2-5 mm, and the thickness of the outer skin is 1-3 mm. A molding method comprises the following steps: (a), pasting a blade handle with the foam core material; (b), feeding prepreg; (c), performing paving and glue suction compaction on the front edge reinforcing area and the main bearing beam; (d), performing paving and glue suction compaction on the inner skin; (e), solidifying; (f), molding the outer skin. According to the invention, the high-performance wind tunnel fan blade can be produced, and the use requirements under low-temperature, high-pressure, high-humidity and normal-temperature vacuum simulated climate environments can be met.