The gamma dose rate radiation model of PN junction which is the fundamental structure of integrated circuit is studied. Firstly, the importance of the PN junction dose rate radiation model is explained. Then, the analytic model of the photocurrent response of one-dimensional uniform doping abrupt PN junction is calculated based on the equation of semiconductor physics. Photocurrent response with different parameters is drawn by Mathematica according to the analytic solution. Results are compared with Technology Computer Aided Design(TCAD) numerical simulation so as to confirm the correction of analytic solution. Finally, through the analysis of the effect of dose rate, bias, PN junction geometry, doping concentration, diffusion coefficient, minority carrier lifetime on steady-state photocurrent, a new model is put forward to calculate the steady-state photocurrent, which could be much more convenient for engineering calculation.