The invention relates to a water-conservancy reservoir investigation sampling device. The water-conservancy reservoir investigation sampling device is characterized in that: the water-conservancy reservoir investigation sampling device comprises a main frame, wherein water carriers are uniformly distributed at the periphery of the outer wall of the main frame, a main gear is arranged at the top part of the main frame, a swinging arm is arranged on the main gear, a pressure wheel is connected at the top part of the swinging arm, a pinion driven to rotate by a motor is meshed on the side edge of the main gear, and a mud sampler is arranged at the inner side of the main frame. Compared with the prior art, the water-conservancy reservoir investigation sampling device has the advantages that: 1. when the soil sampler is pressed to load soil by hydraulic pressure, the bottom surface of the whole device at the water bottom is fixed firmly, and thus sampling can be succeeded; 2. in addition to sampling soil, the device can sample water, therefore, the function of the device is increased; and 3. a mud guard of the soil sampler works stably and can rebound automatically by a spring and can retain the soil sampler.