The invention discloses a silicon-heater-based MEMS (microelectromechanical system) methane sensor and a preparation method thereof, belongs to a methane sensor and a preparation method thereof, and particularly belongs to a methane sensor adopting a microelectromechanical system manufacturing technology and a preparation method and a methane detection method thereof. The methane sensor adopts an ordinary monocrystalline silicon wafer for manufacturing a silicon heater, the silicon heater is used as a methane-sensitive element, and a catalyst carrier and a catalyst material are not required; the preparation method of the methane sensor is compatible with a CMOS (complementary metal oxide semiconductor) technology; in case of batch production, the methane sensors have an advantage of low price and can be calibrated in batches; the methane sensor has the characteristics of low power consumption, high sensitivity , fast response, no influence on methane detection during oxygen shortage, and no influence from carbon deposition, poisoning and catalysts.