The invention discloses a speed regulation design method and device of a differential pressure driven pipeline interior detecting device. The speed regulation design method comprises the steps that a geometric model for drainage flow speed regulation is established based on a single-hole gradually-enlarged structure; a pipeline flow field numerical model of the geometric model is established; the relation between regulation piece expanding degree of the geometric modeland a driving force in a flow field is obtained through simulation analysis conducted on the pipeline flow field numerical model; an expanding degree range during normal working of a regulation piece is determined according to the relation; speed regulation design is conducted on the differential pressure driven pipeline interior detecting device according to the expanding degree range. The arc-shaped triangular regulation piece is designed to serve as a self-balanced type drainage flow speed regulation device of a regulation unit by establishing an interior detector flow field numerical model in a drainage flow state and conducing numerical modeling and force analysis on the model, the driving force of an interior detector can be effectively regulated, and it is achieved that the speed of the driving force reaches a stable state within a short time.