In this paper, the forming property of the interface between glass fibers and polyurethane is studied by using CSLM and IR spectroscopy. Microscopic results show that the dispersed effect of glass fibers in KH550 is quite good, a dense membrane is formed on the glass fibers′surface, and the thickness and uniformity will have influenced on the forming of the regular foamed cell of polyurethane. The results of IR spectroscopy show:NCOand —NH₂ have reacted to be carbamido, the steady interface with chemical bonds is formed. And the mechanic properties of two types of surface modified glass fibers loaded rigid polyurethane foams are investigated, at the same apparent density, the compressive strength has increased spontaneously, while the modulus has a little difference.