A method of controlling chaos is presented by phase conjugation feedback (PCF) in a semiconductor laser. The physical model of controlling chaos produced by modulating the current of semiconductor laser is set up under the condition of PCF. The physical mechanism is found that the nonlinear gain coefficient and linewidth enhancement factor of laser are affected by PCF, the system dynamical behavior and its frequency characterization can be changed and controlled. The effect quantity relates to the feedback coefficient, the delay time and the linewidth enhancement factor. Numerical simulations show that chaos is controlled into the periodic state, the dual-periodic state, the multi-periodic state respectively by controlling PCF light delay time under the conditions of different PCF light intensity. And the laser emitting power is increased by PCF when chaos are controlled in all kinds of periodic states because that the performance characterization of the PCF light can produce the coherent function on the laser emitting light to realize controlling chaos in PCF controlling chaos processes.