The channel current model is used to analyse the behavior of uniaxially strained Si NMOSFET device and circuit. With the development of mobility and threshold voltage model, starting from the basic drift-diffusion equation, the channel current model for an uniaxially strained Si NMOSFET device is developed under different bias conditions. Especially, the stress intensity is explicitly included in the mobility and threshold voltage model, and this makes the model convenient to directly reflect the relationship between the device channel current and the stress intensity. Moreover, in terms of the subthreshold current model, the charge of weak inversion rather than the normal effective channel thickness approximation is involved. In this way, the model accuracy can be improved. Furthermore, this model is implemented by using verilogA language and is applied to the strained Si circuit's SPICE simulation, the model parameters extraction tool ParamPlus++ is developed at the same time. As a result, the simulation of uniaxial-strained Si NMOSFET device and circuit can be achieved; the simulation data fits the experimental results or TCAD simulation results very well, and this proves the accuracy of the model. Meanwhile the simulation results of the threshold voltage and subthreshold current with respect to stress intensity are obtained and analyzed. The results show that with increasing stress intensity the subthreshold current is increased while the threshold voltage is decreased.