The invention relates to the technical field of support devices, in particular to an adjustable support device and an application method thereof. The adjustable support device comprises a base, a sliding trolley, an upper lifting bracket and a connecting truss. The base comprises a bottom bracket, a hydraulic supporting leg and a driving wheel. The bottom bracket comprises two transverse bracketsand two longitudinal brackets. Chutes are formed in the tops of the two transverse brackets in transverse directions. Four pulleys of the sliding trolley are placed in the chutes of the two transversebrackets. Two transverse push-pull rods are connected to the left side of the bottom of the sliding trolley. The upper lifting bracket is connected to the top of the sliding trolley through four electric rods. The connecting truss is connected to the upper lifting bracket through a bolt. By designing the transverse push-pull rods and the electric rod, position of construction equipment can be adjusted finely, so that the construction equipment is positioned precisely. According to the lengthened design of the connecting truss, the down-passing depth of the construction equipment can be adjusted for roughly positioning the construction equipment.