The ways to ensure data security in wireless sensor networks are getting more and more attention from people.This paper proposes a scheme,RWS(Random Watermarking Scheme),that ensure data security based on digital watermark technology.The data from the source node is calculated as the watermark information using the hash function; Then according to the pre-stored key numbers and the processing block,and a combination of a hash function to generate a corresponding watermark storage location in processing block,Finally,the watermark information is embedded in the source data.When the nodes of base station receives the data,the watermark information extracted from each processing block,is compared with the recalculated watermark information,if they are identical in sequence,we deem that the original data is correct and complete,otherwise the data has been destroyed.A large number of network simulation experiments results show that this method has high sensitivity to attacks of selective forwarding,replay; Compared with other methods,RWS has less traffic overhead and a certain hidden information,and it improves network security to a certain extent.