The invention provides a trigger assembly of a street lamp with an automatic umbrella, and relates to the field of public facilities, in particular to improvement of the street lamp provided with the umbrella. The trigger assembly of the street lamp with the automatic umbrella is ingenious in structure, good in stability, high in safety, free of manual control during use, and capable of being turned on and turned off automatically. The trigger assembly is arranged above the umbrella and contained in a lamp pole. The lamp pole is hollow, and a plurality of through holes are formed in the top of the lamp pole. The trigger assembly comprises a fixing seat, a spring, a trigger ball head, a balancing weight and a sponge. The fixing seat is fixedly connected in the lamp pole and located below the multiple through holes. The balancing weight is slidably connected in the lamp pole and located above the fixing seat. The spring is located between the fixing seat and the balancing weight in an abutting mode. The sponge is supported by the top face of the balancing weight, and electric heating wires fixedly connected to the balancing weight are arranged between the balancing weight and the sponge. Manual operation is not needed, the automation degree is high, the reaction rate is high, and safety is good.