How to protect secret information is a most important issue in military technology. In this paper, a (p,n) secret sharing method using Blakley's concept is proposed to protect the security of secret images. Even though enemies know p-1 of n shadow images, they cannot obtain any information about the secret image. Only p or more than p shadow images can reconstruct it. Experimental results show that the proposed method has the advantage of smaller shared images, which can greatly reduce the storage space.