The invention discloses a protective device for an internal component of a diesel generator exhaust gas treatment device. The protective device comprises a base, a component body, a fixing plate, an arc-shaped plate, an annular plate, a limiting rod, a limiting plate, a regulating rod, a sliding block, a limiting spring, a sleeve rod, a torsion spring, a baffle plate, a sliding rod and an L-shapedplate, wherein a placing groove and a groove are formed in the top of the base, and a regulating groove is formed in the base; the component body is arranged at the top of the base; the fixing plateand a placing plate are glidingly connected in the placing groove; and the fixing plate is positioned directly above the placing plate. According to the protective device for the internal component ofthe diesel generator exhaust gas treatment device, by the mutual matching of a limiting groove and the sleeve rod, the sleeve rod drives the annular plate to rotate during sliding, and the fixing plate is limited by the arc-shaped plate; a structure is simple, and operation is convenient; and the time of manual installation is effectively reduced, the stability of the component is improved, and the working efficiency is improved.