The utility model discloses a double-grab bucket type layered sludge sampling device based on an unmanned ship. The double-grab bucket type layered sludge sampling device comprises the unmanned ship and a sampling device, The sampling device is hoisted through an unmanned ship, and is driven by a fan to hover the unmanned ship; The bottom of the unmanned ship is connected with a connecting pipe through a fixing plate; A sampling pipe is arranged outside with the connecting pipe as the center, a cable is arranged in the connecting pipe, double grab buckets are hung on the cable, the double grabbuckets comprise the first grab bucket and the second grab bucket, the first grab bucket is connected into the second grab bucket in a sleeved mode, and the first grab bucket and the second grab bucket are coaxially connected to control grabbing of sludge of different depths for layered sludge sampling. A clamping groove is formed in the sampling pipe, and the double grab buckets are clamped andfixed through the clamping groove in the sampling process, so that sampling is stable. The layered sludge sampling device is simple in structure and convenient to use, layered sludge sampling is carried out through the double grab buckets, sludge samples of different layers on a vertical sludge layer with good integrity can be obtained, and the suspended unmanned ship is controlled and driven to position and collect the sludge samples.