Drainage bag capable of sampling

The utility model relates to the field of drainage bags, in particular to a sampling drainage bag which comprises a bag body, a negative pressure drainage device, a connecting pipe and a sampling bottle. The right lower end of the bag body is hermetically connected with the negative pressure drainage device through the connecting pipe, and the sampling bottle is detachably connected with the negative pressure drainage device; the negative pressure drainage device comprises a first one-way valve, a second one-way valve and an elastic hollow sphere, two ends of the elastic hollow sphere are opened, one end is connected with the first one-way valve, and the other end is connected with the second one-way valve; when drainage liquid flows to the sampling bottle from the bag body, the first one-way valve and the second one-way valve are opened, the check valve is arranged between the second one-way valve and the sampling bottle, and the third one-way valve is arranged at the top end of the sampling bottle, so that