A chain box observation hole sealing mechanism comprises a chain box observation hole, an upper cover plate and a lower bottom plate mounted thereon; a door spindle is mounted at the upper end between a chain box and the upper cover plate; a door lock is mounted at the lower end; at least two baffle plates are mounted on the upper cover plate; at least a baffle plate is mounted on the lower bottom plate; a groove is formed between the baffle plates; and a flow guide hole is formed on the lower bottom plate. The chain box observation hole sealing mechanism has the characteristics of good sealing performance, lubricant conservation, civilized operation and the like, and is widely applied to the sealing technology of observation holes of oil workover rigs or similar mechanical equipment.