The invention discloses a semiconductor lead frame surface treatment method sequentially comprising ultrasonic degreasing, electrolytic degreasing, washing, sulfuric acid neutralization and activation, washing, electro-coppering, washing, acid neutralization, washing, copper protection, washing, hot washing, and drying. The step of copper protection has the following specific technical requirements: a semiconductor lead frame is guided into and immersed in protection liquid to achieve the purpose of making the semiconductor lead frame coated with a copper protective film, wherein the pH of the protection liquid is 5-7, the temperature is 20-40 DEG C, the immersion time is 10-20S, and the protection liquid contains 9-15g/L alkyl benzimidazole and 1-3g/L acetic acid. An organic protective layer is arranged on a copper surface layer to replace a diaphragm layer, and the protective layer is naturally removed during tin dipping and aluminum wire welding. Thus, protection is achieved without affecting the welding effect.