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