In order to solve the problems of data availability, confidentiality and integrity in local heterogeneous networks, a three-stage system design model of terminal detection, data storage access, and secure channel establishment and transmission is proposed. Firstly, the terminal system is scanned and detected to avoid the data unavailability problem caused by attack or incomplete hardware layer cleaning. Secondly, the data encryption storage access and self-destruction mechanism are set to realize the data confidentiality function and eliminate the privacy disclosure problem. Finally, SSL and VPN technologies are used to realize the secure establishment of the channel and the complete and secure transmission of the data. Through the prototype model design and the simulation experiment, the test and analysis are carried out, and the results show that the available precision of terminal detection achieves more than 90%, the encryption speed of the security function is less than 0.5 MB/s, the self-destruction protection mechanism is effective, and the full transmission speed of the channel data is increased by about 275% on average. It can be found that the model can be of high reference value for network data security detection and protection.