The utility model relates to a heat exchanger comprising a shell body which is provided with a heat exchange working substance inlet and a heat exchange working substance outlet; a plurality of layers of serpentine heat exchange tubes with refrigerant inlets and refrigerant outlets; the adjacent two layers of serpentine tubes are staggered; and positioning columns for fixing the serpentine heat exchange tubes are arranged in the shell body. According to the heat exchanger, different layers of heat exchange tubes are staggered in a mesh shape, so that the disturbance of fluid on a shell body is greatly improved, and even at lower flow rate, the disturbance of fluid which flows around outside the tubes can be effectively enhanced, so that the heat transfer coefficient of the fluid on the shell side and the heat transfer performance of the heat exchanger are greatly improved, and the temperature distribution of the fluid on the shell side is more uniform; and in addition, a spoiler, a diversion column and other parts which are commonly used in the prior art are omitted; simultaneously, the alternative flowing method on the shell side is changed into the flowing method outside the tubes with smaller resistance, so that the process duration of the fluid on the shell side is reduced, the flowing resistance on the shell side is effectively reduced, the pump power consumption of a system is reduced, and energy is saved.