The invention discloses a formula of a high-strength polyester composite well cover, which comprises the following raw materials in parts by weight: 21-22 parts of unsaturated polyester resin, 8-9 parts of low shrink additive, 40-50 parts of heavy calcium carbonate, 1-1.5 parts of zinc stearate, 0.2-0.8 part of active magnesia, 0.12-0.28 part of curing agent, 0.2-0.8 part of carbon black, 10-20 parts of alkali-free glass fiber roving and 10-20 parts of glass fiber woven roving. A production method of the well cover of the invention comprises the following steps of: firstly preparing resin paste, preparing sheets by utilizing the resin paste, and then, forming the sheets by die pressing. The well cover of the invention has the characteristics of strong carrying capacity, shock resistance, ageing resistance, wear resistance, corrosion resistance, novel and attractive appearance, simple structure, environmental protection and the like, and basically solves the problem of well cover pilfering.