This paper describes a new product, the flame-proof variable-frequency induction motor used in coal mine. The motor is integrated with frequency converter to meet the requirement of high efficiency and energy conservation. According to the traditional electromagnetism calculation program, we add a new method for the variable-frequency motor, combine this method with ANSOFT 2D finite element to analyze and examine it, give a particular description of the frequency conversion motor principle and control tactic, provide a sample motor and introduce its design and manufacture technology.