The invention belongs to the technical field of gate sealing and leakage monitoring and specifically relates to an apparatus for monitoring the sealing and leakage of a gate of double-layer containment vessel equipment in order to solve problems of invisible logic implementation and poor maintainability of an original control system. The apparatus comprises a CPU module, an expansion module, a display unit, an inflating solenoid valve A, an inflating solenoid valve B, a pressure testing device A, a pressure testing device B, and an OM display unit. The display unit, the inflating solenoid valve A, the inflating solenoid valve B, and the expansion module are connected with the CPU module. The pressure testing device A and the pressure testing device B are connected with the expansion module. The apparatus achieves a function of monitoring the sealing and the leakage of the gate and has characteristics of good maintainability, high system operation reliability, low cost, easy purchase of spare units and parts because being independent of an equipment gate control system. The apparatus for monitoring the sealing and leakage of the gate of double-layer containment vessel equipment provides guarantee for nuclear security of a unit.