The invention provides a small-scale blind cavity inner wall surface purifying and descaling device. The device comprises a cleaning liquid supply unit, a cleaning liquid recovery unit, a gas supercharge unit, a cleaning execution unit and a mechanical support structure, wherein the four units are connected through pipelines; valves on the pipelines control on and off of all the units; the four units are all mounted on the mechanical support structure; the cleaning liquid supply unit is used for supplying cleaning liquid to the cleaning execution unit; the cleaning liquid recovery unit is used for recovering the remaining cleaning liquid; the gas supercharge unit is used for adjusting the pressure of input gas to realize the cleaning of different degrees; the cleaning execution unit is used for realizing the cleaning of multiple modes; and the mechanical support structure is used for fixing, positioning, mounting and supporting the whole device. The device is high in automation degree, convenient to use and high in cleaning efficiency, and can be widely applied to the purification and the descaling of an inner cavity of a small instrument.