The invention discloses a testing device and method for simulating ground loss triggered by a subway shield tunnel stratum cavity. The testing device comprises a visual identification system, a model box system, a poly-chloramine sac (11), a first guide pipe (12) and a second guide pipe (21) which are communicated with the poly-chloramine sac (11), a container (17) corresponding to the second guide pipe (21), a resistance wire (13) arranged inside the poly-chloramine sac (11) and a heating control device (20) connected with the resistance wire, wherein the visual identification system comprises a real-time monitoring camera (1), a fixing support (2) and an acquisition and calculation module (3); the real-time monitoring camera (1) is used for shooting a video image of a monitoring interface; the video image is transmitted to the acquisition and calculation module (3) to be analyzed and calculated so as to obtain displacement data of an interest point; the testing device further comprises a purdah (4) for covering the whole testing device and light sources (5) fixed in position. According to the device, the sedimentation of each particle in the developing process can be monitored in real time.