The present invention provides a method of detecting water heater safety, wherein the water heater includes a blower and a combustor. The method includes starting the blower and detecting blower speed after a certain amount of time; comparing the blower speed with a first speed range, and then supplying gas to the combustor when the speed of the blower is within the first speed range, or providing an alarm when the blower speed is beyond the first speed range; detecting the speed of the blower again after the combustor heats water for a time; comparing blower speed with a second first speed range, and then supplying gas to the combustor when the blower speed is within the second speed range, or stopping gas when the blower speed is beyond the second speed range.