The invention discloses a protecting device for a microearthquake acquisition system in a complex environment. An indicator light and a waterproof aerial socket are arranged on a tank cover. The tank cover is fixed to an inner support. The inner support comprises support arms connected with the tank cover and a fixing plate connected with the support arms. A positioning plate is arranged on the tank cover. A clamping strip groove is formed in the positioning plate. The face, making contact with a tank body, of the tank cover is provided with a convex strip. A tank body groove is formed in a tank opening of the tank body. The convex strip is embedded into the tank body groove. A clamping strip is longitudinally arranged on the inner wall of the tank body. A pair of clamping sheets is arranged in the tank body. The top end of the clamping strip is clamped into the clamping strip groove, and the fixing plate is clamped between the clamping sheets. A fixed circuit board screw hole, a circuit board connecting screw hole and a reserved screw hole are formed in the fixing plate, and a silica gel sealing strip is arranged between the convex strip and the tank body groove. The protecting device is low in mass and good in heat conduction, electric conduction and impact resistance; the indicator light is well sealed; entering of water, moisture and dust is effectively avoided; further reinforcement is achieved through the clamping sheets and clamping strip in the tank body, and damage is not likely to happen.