Metal oxide semiconductor (MOS) gas sensors require their sensing materials to operate at temperatures ranging from 200℃ to 500℃ to achieve sufficient and controllable chemical reactions with target gases. Micro-electro mechanical systems (MEMS) technology enables the monolithic integration of gas-sensitive films, heaters, and signal processing circuits on a single chip, significantly reducing power consumption and device size. Among these components, the micro-heater, which provides a stable operating temperature for the gas sensor, plays a crucial role in determining the overall sensor performance. The electrode morphology, dimensions, and materials of the micro-heater directly influence key characteristics such as temperature distribution, power consumption, and mechanical stress. Furthermore, the temperature uniformity, operating range, thermal response time, power efficiency, and mechanical stability of the micro-heater collectively affect the sensitivity, selectivity, lifetime, and reliability of the sensor. This review focuses on recent advances in micro-heater design over the past five years and examines how optimized designs impact sensor performance. Firstly, the gas-sensing mechanism of semiconductor materials and the influence of operating temperature on sensor performance are introduced. Based on this, the theoretical foundations of heat conduction, convection, and radiation in micro-heaters are presented, along with various modeling and optimization approaches. Secondly, recent research progress on the morphological and structural design of micro-heaters is elaborated, covering geometric configurations, thermal isolation structures, suspension beam optimization, and micro-hotplate arrays. The effects of these structural improvements on gas-sensing performance are also discussed. Subsequently, different materials used in micro-heater fabrication are reviewed, with an evaluation of their mechanical stability and electrothermal properties. Finally, the current research status and key performance parameters are summarized, and future research directions are outlined, providing insights for enhancing semiconductor gas sensor performance through micro-heater optimization.