The invention provides an auxiliary alarming device of a railway grade crossing. The auxiliary alarming device comprises infrared detector sets and an alarm unit, wherein the infrared detector sets comprise a first detector set and a second detector set, the first detector set is arranged on a roadway gate of the crossing, crossing space, 300mm-800mm vertically away from the ground, below the roadway gate is detected, and the alarm unit is controlled to give an alarm when it is detected that people exist; the second detector set is arranged on the ground on two sides of a rail of the crossing, crossing space, with the vertical distance from the ground to the top of a steel rail being 300mm, below the roadway gate is detected, and the alarm unit is controlled to give an alarm when it is detected that an obstacle exists. The auxiliary alarming device is simple in structure, significant in effect, direct and high in efficiency, enhances railway grade crossing alarming functions, improves highway and railway safety conditions, and further improves safety performance of the railway grade crossing; meanwhile, it is guaranteed that transport capacity of the railway can be improved and safe and punctual running transportation is achieved.