The invention discloses a cavity type prevention device for tunnel bottom deformation of a ballastless track, and a construction method of the cavity type prevention device. The cavity type preventiondevice comprises cavity chambers formed in an inverted arch filling layer, and a plurality of vertical columns are further arranged inside the cavity chambers. The construction method comprises the steps that reinforcement cages of the inverted arch filling layer are bound; a plurality of inner formworks are arranged in the inverted arch filling layer in the longitudinal direction of a tunnel, sothat all the inner formworks form the required cavity chambers of a plurality of closed areas; and the inverted arch filling layer is poured, so that the inverted arch filling layer with the cavity chambers is formed. Through forming of the cavity chambers, a sufficiently large deformation space can be provided for tunnel bottom surrounding rock, the surrounding rock volume increment caused by surrounding rock stress adjusting can be counteracted by utilizing the cavity structures, and the situation that the surrounding rock volume increment directly affects a top plate of the inverted arch filling layer, and consequently the tunnel bottom arches upwards and is not smooth is avoided; and the cavity chambers play the roles of stress releasing and reducing of damage of the tunnel base loadto a tunnel inverted arch in the operation period simultaneously.