With the rapid development of the photovoltaic industry, the data security problem is becoming more and more prominent, and the endogenous security mechanism, as a kind of active defense means, can effectively improve the security and reliability of photovoltaic data. This paper proposes an endogenous security defense system for PV data transmission and storage. First, a LoRa-based PV power plant data transmission system is constructed on the PV transmission side, and a hybrid encryption mechanism is designed to reduce the security risks during data transmission. Second, on the PV data storage side, a distributed transmission protocol and hash consistency detection method are used to complete the group storage of PV data. Then, in order to further optimize the data security defense, trusted security architecture and data desensitization mechanism are used to secure the stored PV data. The test found that the security posture assessment of the endogenous security defense system designed based on the method of this paper has good beam pointing and can accurately reflect the final distribution of the security posture after being subjected to security threats.