The invention discloses a gas burner used in a water heater. The gas burner comprises the water heater and a burner body, wherein the bottom of the burner body is in threaded connection with the innerwall of the water heater through bolts; and the burner body comprises a mounting base, the top of the mounting base is welded with a shell, an air blower is fixedly installed on one side of the shell, and the side, close to the air blower, of the interior of the shell is in threaded connection with an air blowing plate structure through bolts. The gas burner can guarantee that the primary air coefficient is within the range of 0.5-0.7, clear, transparent and obviously blue combustion flame can be obtained under appropriate air blowing conditions, and the content of CO in the flue gas is below300PPm and is much lower than 600PPm stipulated by national standards; at the same time, heat exchange is full, and the heat efficiency is higher than 88%, higher than 80% of specified national standards, and 2% ~ 5% higher than the same type; high power combustion can be achieved through the structure, the cost of the gas burner is greatly reduced, and the gas burner is suitable for promotion and popularization.