Abstract: The influence of average heating temperature, belt speed, feeding rate on five-layer mesh belt hot air drying of onion was studied. On the basis of single factor experiment, Box-Benhnken experiment was used to establish a quadratic regression equation with average heating temperature, belt speed and feeding rate as influencing factors, water content, drying yield and color-optical index comprehensive score as response values. The results showed that comprehensive score of onion was influenced in decreasing order by heating temperature, belt speed and feeding rate. The optimum condition for five-layer mesh belt hot air drying of onion was: heating temperature, 70℃;belt speed, 10 cm/min;and feeding rate, 1200 kg/h. Under these conditions, the response value was 82. 02, agreeing with the predicted value(82.32), indicating that the optimization result was reliable.