Abstract: Based on the superposition and interference theory of waves，when an extreme value of light intensity

is parallel，the related formulas of the intensity distribution of interference field and the contrast degree of the interference

fringe by two partially polarized lights are obtained. The formulas can be applied to various interference

processes in which natural light，linear polarized light and partial polarized light composed of them participate. On

　　the basis of these，the interference field of different polarization state light such as line polarized light and line polarized

　　light，natural light and natural light，line polarized light and natural light are analyzed in detail. The specific

　　expressions of light intensity distribution of interference field and contrast degree of the interference fringes are given.

　　The conclusions are of great significance to recognition of interference field of the aforementioned polarization

　　states and to improvement of the contrast degree of interference fringes of the corresponding interference field in the

　　interferometer.

Key words: partially polarized light, intensity distribution of interference field, contrast degree of interference fringes