The invention discloses a double-sensor combined detector and method for detecting combustible gas and steam, which solves the problems that when a single sensor is used for detecting the combustiblegas and steam in the prior art, intelligent monitoring cannot be realized, and the single sensor is generally influenced by measuring range, linearity, service life and the like and cannot play a safety monitoring role well. According to the invention, a semiconductor gas sensor and a catalytic combustion type gas sensor are used alternately to detect combustible gas and steam, the semiconductor gas sensor is used for detecting the combustible gas and steam with low measuring range, when the concentration of the combustible gas and steam in the environment exceeds the threshold value detectedby the semiconductor gas sensor, the voltage output of the catalytic combustion type gas sensor is started, the concentration is calculated and used as the final concentration output of the detector.The double-sensor combined detector and method for detecting the combustible gas and steam can realize the fault detection of the detector, prolong the service life and give full play to the advantages of the semiconductor gas sensor and the catalytic combustion type gas sensor, thereby greatly reducing the maintenance cost of users.