The invention discloses a dangerous medium flash evaporation mist spray two-phase flow and atomization generating device and a testing method. The dangerous medium flash evaporation mist spray two-phase flow and atomization generating device comprises a flash evaporation mist spray generating system, an integrated control system and a testing system. The flash evaporation mist spray generating system is characterized in that a high-pressure nitrogen cylinder communicates with a gas phase inlet in the upper part of a working medium storage tank; a liquid phase outlet in the lower part of the working medium storage tank communicates with the center of an upper cover of a temperature-control pressure-control cavity; the center of the bottom surface of the temperature-control pressure-controlcavity is directly connected with inlets of electromagnetic valves; outlets of the electromagnetic valves are connected with nozzles; the integrated control system is connected with equipment in othersystems through external wires, and hardware is integrated in an integrated control box. The device is controlled through a design program, accurate adjustment and synchronous collection of parameters in the flash evaporation generating system are achieved through the integrated control system, synchronous measurement of fog field parameters by all devices of the testing system is achieved, safeand stable operation of the device is ensured through the safety auxiliary system, and research on various dangerous media is achieved.