Reducing and repeated-use reserved opening building device

The invention relates to building equipment, in particular to a reducing and repeated-use reserved opening building device. A fixing mechanism axially passes through the center of a sleeve to fix the sleeve on a template, and a cover plate covers an upper opening of the sleeve; the fixing mechanism comprises a vertical rod, cross arms, a nut, a horizontal circular ring and a fixing hook, wherein the lower end of the vertical rod is fixedly connected with the center of the horizontal circular ring after passing through the cross arms, the fixing hook is sleeved on the horizontal circular ring, the lower part of the fixing hook is fixed on the template, the nut is installed on the vertical rod on the cross arms, and the upper opening of the sleeve is radially provided with two grooves in which the cross arms are placed. The reserved opening building device has the advantages of simple structure, is convenient to construct and disassembly and can improve construction quality.