The invention discloses a loess tunnel construction supporting device. The loess tunnel construction supporting device structurally comprises buried bases, motors, a pressurizing structure, supportingcolumns, an arch beam, a cross beam, a fixed mounting base and decompression mechanisms, wherein the supporting columns are vertically arranged at the two ends of the arch beam; the end, away from the arch beam, of each supporting column is also provided with one buried base; the two ends of the arch beam are also mechanically connected through the cross beam, the fixed mounting base is vertically welded to the top surface of the cross beam, and the decompression mechanisms are arranged at the two ends of the fixed mounting base. The device is provided with the supporting columns, the pressurizing structure and the decompression mechanisms; the supporting columns are buried deeply, so that the stress area is increased, and the stability of a base is directly improved; meanwhile, the pressure intensity of the supporting columns, the arch beam and the cross beam is increased, and the phenomena that the supporting force is weak and inward sliding happens are not likely to occur; meanwhile, the decompression mechanisms bear the load of upper-layer loess, load pressure relief is carried out according to the force balance principle, the overall pressure of the supporting columns is reduced, and the service life of the device is prolonged.