An effective method for reducing the speckle noise in digital holography is proposed in this paper. Different from the methods based on classical filtering technique, it utilizes the multiple holograms which are generated by rotating the illuminating light continuously. The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns. Hence by properly averaging the reconstructed intensity fields, the speckle noises can be reduced greatly. Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.