The increasing number of smart phone users together with the mobile communication and social network technology improvement lead to multi-functional services, such as realtime multimedia content sharing, Location-Based Service (LBS) and Geo-Social Networks (GeoSNs). However, the issues of multimedia content sharing with location-related privacy in GeoSNs start to be investigated and the security solution is yet to be found. Therefore, we propose a secure mobile multimedia content sharing service (SMM-CSS) which includes mobile users (MUs) and GeoSNs. To address the security concern, SMM-CSS has applied the Network Coding (NC) and Homomorphic Encryption (HE) techniques to support the secure multimedia transmission. Under such mechanism, personal location and social network relationship can be managed for secure communication. In addition, the architecture can be easily implemented to the existing GeoSNs.