Abstract: Using camplastometer with high and constant strain rate the flow stress of low carbon nio-birm containing (Nb 0%~0.12%) steels has been investigated. The deformation Temp, are 750°~1150℃, strain rate are 5~80s^-1, acount deformation 0.06~0.69. The effects of Niobium content, T, ε and ε on the flow stress of steel were analysised, and a model of flow stress for these steels with precise draft were established. This model can be used for computer control in rolling mill.