Abstract: Considering the depolarization of polarizer, the Malus law is extended and the physical model of transmitted light intensity of natural light through two non-ideal polarizers is established and tested. The experimental results show that the physical model coincides well with the experimental data and has significantly reduced the experimental error, which is only about 5% , in the general physics experiment ＂Verification of Malus Law＂. The principle of this model is simple and the physical image is very clear, so it is a good simplified model coincidence well with the experiment. It can help to reduce laboratory maintenance costs, broaden students critical thinking and cultivate students the quality of innovation.

Key words: Malus law, polarizer, depolarization