A hybrid solar drying system assisted by heat pump for grain in-store drying was developed. The system is composed of solar air collector, heat pump and stir machine for grain. The experimental study was conducted for maize drying. The results indicated that average thermal efficiency of the air collector is up to 63% and COP of the heat pump can reach 5.4. The combined system can supply adequate and stable thermal energy. The effect of drying is obvious. Drying time is reduced and energy consumption is low. Besides, the uniformity of moist content is improved. Utilized for maize in-store drying, the system can reduce the moisture content of maize in the granary with the characteristics of safety, energy saving and better effect.