The invention discloses an alkali activated slag cement concrete prefabricated inspection well lid and a preparation process thereof. The inspection well lid is prepared from granulated blast-furnace slags, cement clinkers, retarders, sand, stone, steel fiber, water and sodium silicate. The preparation process comprises the following steps: in parts by weight, premixing granulated blast-furnace slags, cement clinkers, retarders, sand and stone in a mixer for 2-3 minutes; then, adding steel fiber by using a vibrating screen, and mixing the obtained mixture; adding water and sodium silicate by using a funnel; after mixing the obtained product, pouring the obtained product into an iron well-lid mould; after carrying out standing for 2-3 hours at room temperature, placing the obtained product into a steam curing chamber at a temperature of 75-85 DEG C to carry out curing for 2-3 days; and after carrying out natural cooling demoulding, carrying out watering and film covering on the obtained product to cure 7 for days. According to the invention, by using the excellent mechanical properties and durability properties of alkali activated slags, the impact-resistant and bending-resistant properties of the well lid are enhanced through mixing steel fibers with different lengths, and an alkali activated slag composite prefabricated round plate which is low in cost, light in weight and high in performance is prepared for replacing an iron inspection well lid, thereby solving the problem that an urban inspection well lid is stolen.