A real-time video transmission algorithm using double dynamic buffers and double operation threads based on TCP protocol is proposed according to the characteristics of video stream and real-time surveillance applications.One video data buffer and one data sending buffer,which are managed respectively by one video data storing thread and one data sending thread,are set up in the transmitter.The video data storing thread dynamically adjusts the video data buffer size and discards some video frames selectively during network congestion according to the maximal time waiting for sending and the network data transmission speed calculated actually in the data sending thread.The data sending thread sends video data to receiver and obtains video data one frame by one frame from the video data buffer,and calculates the network real-time data transmission speed.The experiment in simulated environment is given at last.The results show that the proposed algorithm is able to utilize network variable bandwidth in the greatest extent for transmitting video to receiver by real-time and ensures to play back smoothly in receiver,and can be applied effectively for real-time video surveillance in narrow and variable bandwidth networks.