The utility model discloses a subsurface excavation tunnel top bracing device adopting lifting jacks for movable support. The device comprises a primary support structure and a top bracing structure, wherein the top bracing device comprises a plurality of lifting jacks which are arranged above tops of longitudinal beams of the primary support structure, and a support beam in the horizontal direction is propped and supported at the tops of the lifting jacks. The subsurface excavation tunnel top bracing device adopting the lifting jacks for movable support has the characteristics of high strength, high rigidity and high crush resistance and bending resistance, and by means of the arranged top bracing structure, the mechanical property can effectively applied.