To optimize the preparation process of soy milk powder, the soy milk was used as raw material to prepare soy milk powder through the soybean milk with low purine firstly and spaying dry method. Ultimately, the quality of the prepared soy milk powder was evaluated. The best inlet temperature was 185℃, the feed rate was 16 mL/min, the solid content was 10%, the dry powder rate was 66.18%, the Total purine content of Low Purine Soybean Milk Instant Powder was 100.34mg/100g, reduced by 48.80%. Meanwhile the Sensory, physicochemical and microbiological indexes all meet the requirements of the relevant standards.