Abstract: An image transmission system based on UDP and an adaptive algorithm for control parameters in the system are researched. The new image transmission system based on UDP transmits an image by two independent asynchronous channels (content channel and control channel). The control channel can get control parameters by analyzing result of transmission. The system controls image transmission in the content channel by the control parameters. The system adjusts the control parameters (such as compressing algorithms, size of data package, times of data re-transmitted, etc.) according to the changes of condition parameters (such as network delay, rate of losing data package, times of losing data package continually, etc.) automatically, so that the speed and quality of image transmission are both satisfied. Tests showed that the optimal value of control parameters calculated by the system is close to that measured by experiments.