The invention provides a real-time observation and testing device for simulating foam-based VES acid etching crack, which comprises a water storage tank, an acid storage tank, a foam generator, a gassource, a foam observation chamber, a heating rod, a guide chamber, a press, a thermotank, three back pressure valves, three waste liquid tanks and three analytical balance, three pressure sensors. The foam generator generates a foam-based VES acid according to the water pumped from the water storage tank, the acid liquid pumped from the acid storage tank and the gas injected by gas source; the foam quality and the stability properties of the foam-based VES acid generated before the experiment are observed in the foam observation chamber, and the foam properties of the foam-based VES acid aremonitored in real time in the experiment process; the acid etching experiment of the core sample is carried out according to the injected foam-based VES acid. The scheme can simulate and monitor the formation process and acid etching process of the foam-based VES acid under real underground conditions.