The invention provides an application method of a device for cleaning escalators. The method comprises the following steps: (S1) operators position a step pedal dust removing module on a first-step pedal plate; after a hydraulic lifting rod adjusts a set distance between a cover body of the step pedal dust removing module and the pedal plate, a brush module in the cover body is exposed out of thecover body and contacted with the pedal plate; and the cover body cannot move along with pedals of the escalators during cleaning of the pedals; (S2) an extension cylinder is adjusted to position an armrest belt cleaning module on armrest belts of the escalators; limiting covers transversely cover the escalator belts of the escalators; and four suckers in the limiting covers are absorbed on steelplates below the escalators at the same time; and (S3) the step pedal dust removing module and the armrest belt cleaning module respectively perform dedusting on the pedals of the escalators and cleaning on the armrest belts of the escalators at the same time. The method can perform dedusting on the pedals of the escalators and cleaning on the armrest belts to bring convenience for users to use.