The invention discloses a 
sewage well lid capable of changing hole 
diameter according to the rainwater flow, and relates to the technical field of well lids. The 
sewage well lid comprises a foundation; the middle of the foundation is movably connected with a well lid body, the middle of the well lid body is provided with a 
water storage tank, the middle of the 
water storage tank is movably connected with a floating block, a 
dielectric plate is fixedly connected to the middle of the floating block, a 
water leakage hole penetrating through and extending to the bottom of the well lid body is formed in the bottom of the 
water storage tank, and 
electrode plates are fixedly connected to the two sides, close to the 
water storage tank, of the inner wall of the well lid body. According to the 
sewage well lid capable of changing the hole 
diameter according to the rainwater flow, through cooperative use of an 
electromagnet and a magnetic block, when accumulated water is increased, the 
magnetism of the 
electromagnet is gradually increased, due to the fact that the 
magnetism of the inner side of the magnetic block is opposite to the 
magnetism of the outer side of the 
electromagnet, the magneticblock can drive a blocking block to move inwards under the magnetic attraction effect of the electromagnet; therefore, the 
diameter of a drainage hole is changed along with the accumulated water amount, the 
drainage amount is effectively changed, and the accumulated water problem is effectively solved.