The invention discloses a construction method of a reinforced concrete airtight wall and an application of the construction method. The construction method comprises the following steps of mould hole punching and erecting, rib hole placing, rib distributing, formwork erecting, drainage pipe mounting, cement brick wall laying, slurry plastering, wall bracing arranging and the like. The construction method can be used for construction of an airtight wall when a goaf is filled through a downward horizontal layered road approaching type cementing filling mining method. Raw materials for constructing the airtight wall are common building materials, special machining is not needed, the construction process is simple, the professional skill requirement for constructors is not high, operability is high, the using materials are transported to a site, construction of the airtight wall (not comprising hollow brick building top sealing) can be completed through 2 workers within 8 hours, and the problems that currently, when an airtight wall is constructed, labor and time are wasted, safety and reliability are poor, the economic cost is high, and spread of sudden accidents cannot be quickly and effectively restrained are solved.