A new rate-distortion model of H.264 encoder was firstly set up according to the rate distortion（R-D） charac-teristics of H.264.Then

the end-to-end video transmission distortion was analyzed and based on the R-D model of the H.264 encoder and the error combat characteristics of the Turbo code

an adaptive joint source channel coding（JSCC） over wireless channel was proposed

which could optimize the rate allocation of the available network bandwidth be-tween source coding and channel coding adaptively according to the actual condition of current wireless channel

so as to improve the robustness of the video transmission.The experiment results indicate that

compared with fix choice of channel coding rate

the proposed JSCC scheme is can greatly improve the transmission robustness and achieve better reconstructed video quality at the receiver.