The origin of synthetic fiber's application It's well-known that concrete is the man-made building material used most in engineering at present. However, there are some defects of it, such as easy to plastic constrain and crack, weak tensile strength, bad tenacity, etc. that affect engineering construction. The crack of concrete is ubiquitous that affect not only the rigidity and appearance, but also the endurance of concrete. Rigidity is generally taken as a standard to weigh the material's quality in common concrete project. But those concrete in accordance with design standard of rigidity fail to work in using period designed for inner crack extension or external environment factors. This so-called destruction of endurance often results to accidents or a lot of repairing charge. Small cracks in concrete are also the direct reason of weak tensile strength and many destruction of endurance. Plastic constraint and cracking of cement concrete has been a tough matter in projects as it often occurs during checking and acceptance period of project, greatly affects project quality and is difficult to deal with.