Plastic scintillation detector should be calibrated before using it. Therefore, this paper provides a practical and simple method to calibrate plastic scintillation detectors based on Monte Carlo simulation. Firstly, the responses of the plastic scintillation detector to gamma rays with different Gaussian Energy Broadening are simulated, and then the relationship between Gaussian Energy Broadening and shape of gamma ray energy spectrum is obtained. Secondly the energy spectrum meeting experiment can be simulated according to the relationship above. Then the information of energy spectrum acquired from experiment is confirmed with simulated energy spectrum, the plastic scintillation detector can be calibrated. Two radiation sources 22Na and 137Cs are applied to calibrate plastic scintillation detector in experiment based on this method.