Mud surface position meter and measuring method thereof

The invention discloses a mud level gauge and a measuring method thereof. The mud level gauge comprises a take-up and pay-off structure, a take-up and pay-off line, a fixed pulley and a stress pulley. The take-up and pay-off line crosses the upper end of the fixed pulley, so that the tail end of the take-up and pay-off line is vertically downward, the tail end of the take-up and pay-off line is fixedly connected with a hanging object, the stress pulley is located between the fixed pulley and the take-up and pay-off structure, and the take-up and pay-off line crosses the lower end of the stress pulley, so that the take-up and pay-off line forms an included angle at the stress pulley; the take-up and pay-off line is released through the take-up and pay-off line structure, and the length of the released take-up and pay-off line is the height from the mud surface to the water surface after the hanging object is just immersed under the water surface The height from the sludge surface to the water surface of the sl