The purpose of this paper is to explore difference between the first thermal ignition and the secondary thermal ignition, and to reveal the variation rules of characteristic parameters and critical condition ignition for the secondary thermal ignition of gasoline-air mixture. In this paper, experimental investigation on the gasoline-air mixture secondary ignition induced by hot wall in model underground oil depots tunnel has been carried out. Compared to the first thermal ignition, the ignition intensity of the secondary thermal ignition is greater, while the ignition delay and duration are shorter. After the first thermal ignition extinguish, if the ambient temperature is in the range of 286K to 463K and hot wall’ temperature is in the range of 730 to 783K, then the relation between critical ignition temperature and the ambient temperature can be expressed by cubic polynomial. The critical ignition concentration of gasoline vapor is only 0.45% and that of oxygen is 10.4%.