Based on the rank C70 high strength concrete, the experiments of the cubic compression, splitting tensile and four-point bending for four kinds of ultra high molecular weight polyethylene (UHMWPE) concrete with different fiber contents were conducted to research the effects of the fiber content on mechanical properties of concrete. The results show that the enhancement effect of the UHMWPE fiber on the compressive strength of concrete is not obvious. However, the added UHMWPE fiber greatly improves the splitting tensile strength and bending strength of concrete and it has excellent effects on toughness and crack resistance of concrete. The splitting tensile strength increases more than 25% when the fiber content is between 0.3% and 0.5%; the bending strength increases more than 23% when the fiber content is 0.5%.