This paper proposed a new mix design method of ultra-high performance concrete (UHPC) based on the maximum particle packing density, and the modified Andreasen & Andersen particle packing model was used to calculate the quartz sand grading. Density test and single variable trial-mixing test were employed to design the remain parameters of the concrete mixture, and one group of mix proportion with better strength and fluidity was selected based on the test results. Then, the compressive and uniaxial tensile tests were performed to study the compressive strength and the influence of fiber volume content on the tensile characteristic of UHPC. The test results show that: the compressive strength of UHPC is between 116.64 MPa and 134.85 MPa, tensile strength is between 4.761 MPa and 8.504 MPa, and the tensile strength and toughness increase greatly with the increase of fiber volume content. Additionally, the brittleness failure mode transfers into ductile failure. The results of this paper provide a reference for the application of this kind of materials.