The vector network analyzer is an essential instrument in RF and microwave testing. The traditional methods of detection necessitate the presence of on-site personnel for operation and control, which is inefficient and inflexible, failing to meet the contemporary requirements for intelligent and convenient electronic measurement. To address these challenges, an online software system based on a cloud server was designed for vector network analyzer. The system connects the vector network analyzer to a local computer via the SCPI protocol. The local computer uploads the S-parameters, comprising frequency points, real and imaginary components, to the cloud server's MySQL database via SSH. The Django-developed website allows users to access real-time visual data of S-parameters, including frequency domain, time domain, and standing wave ratio graphs, from any device. The system was tested on the E5071C vector network analyzer for dual-port S-parameter detection of rectangular stainless steel tubes from 10GHz to 12GHz. Results showed no data loss during multiple transmissions between the instrument and the local computer. The error between S-parameter data and the instrument's detection results was less than 0.01%. Users could access real-time S-parameter waveforms simultaneously from multiple devices, proving the system's practicality and providing a reliable solution for vector network analyzer detection.