In order to describe scanning facula temperature field and its characteristic exactly, the forming progress of scanning facula temperature field is analyzed in this paper, and the math model of the temperature field of point heat source scanning and superposing in the facula of laser repeating scanning line is built by applying the superposing principle of the temperature field,and the value simulation and figure description are given. The relationship between parameter and temperature distribution is studied, the result shows that the temperature field of scanning facula has obvious speciality similar to skin effect. The speciality is the theoretical basis for that wide band surface treatment can be done on material by laser scanning rotating mirror with lower laser power. The research method used is applicable to other temperature field that has the character of scanning and superposing process.