Rate　control　plays　an　important　role　in　video　coding　and　transmission.　In　this　paper,　instead　of　using　rate-distortion　(R-D)　model　to　perform　rate　control　as　many　existing　methods　do,　a　rate-quality　(R-Q)　model　of　H.264/AVC　has　first　been　proposed　to　represent　the　coding　characteristics　of　H.264,　where　PSNR　(Peak　Signal-to-Noise　Ratio)　is　used　to　represent　the　reconstructed　video　quality.　Then　a　H.264　rate　control　method　at　frame　layer　has　been　presented　based　on　the　proposed　R-Q　model.　In　this　method,　the　quantization　parameter　(i.e.　quantization　step)　of　the　current　frame　is　determined　by　the　proposed　R-Q　model　according　to　the　coding　statistics　of　the　previous　coded　frames.　The　experimental　results　show　that,　compared　with　the　rate　control　algorithm　of　JM86　reference　software,　the　output　bit　rate　achieved　by　our　proposed　one　is　more　close　to　the　target　bit　rate　while　the　reconstructed　quality　is　comparable.