Optical fiber peg-top space applied light combination structure has a perpendicular configuration reality and its side faces are vertical with the underside. The outside of two side faces and the inside of underside are the fixing plane to three peg-tops. The rest side faces use to fix the electrical source box and cube mirror. The three peg-tops are perpendicular setting, and the peg-top of x axis and y axis is fixed on the outside of the reality side faces, the peg-top of z axis is fixed on the inside of the reality underside. Their fixing surfaces contact completely to increase the heat exchange area of the peg-top to reduce the heat resistance effectively. The three joining pieces connecting with peg-tops fix on one joining piece plane and put the three joining piece planes into one toconnect with the jack of the reality connecting with system. The three peg-tops can debug alone and this is fit for fixing and maintenance the optical fiber peg-top. It is suitable for the gesture controlling of the space aerocraft with small volume, light weight, little heat resistance, high reliability security, well diathermancy.