The invention provides an automatic detector for the analysis speed of coal gas, and the automatic detector comprises an acquisition module, a master control module and an external memory module which are encapsulated into a whole, wherein the acquisition module comprises n gas flow sensors which have the same detection accuracy and different measuring ranges; each gas flow sensor is switched according to the sequence of the measuring ranges in a descending order; the n is larger than or equal to 2, and the n is a natural number; the gas flow sensors collect the gas flow from a coal sampling pot; the master control module presets the analysis speed range of the gas, obtains the real-time analysis speed of the gas and the accumulated flow of the gas and determines a working gas flow sensor; and the external memory module stores the flow of the gas, the acquisition time, the real-time analysis speed of the gas and the accumulated flow of the gas. The detector provided by the invention has the characteristics of high detection accuracy, strong field adaptability and the like, and can be widely applied to the acquisition industries of coal mines and the like.