In this paper, a centimeter-scale monolayer molybdenum disulfide (MoS2) film deposition method has been developed through a simple low-pressure chemical vapor deposition (LPCVD) growth system. The growth pressure dependence on film quality is investigated in this LPCVD system. The layer nature, electrical characteristic of the as-grown MoS2 films indicate that high quality films have been achieved. In addition, a hydrofluoric acid treated SiO2/Si substrate is used to improve the quality of the MoS2 films. Piezoresistive strain sensor based on the monolayer MoS2 film elements is fabricated by directly patterning metal contact pads on MoS2 films through a silicon stencil mask. A gauge factor of 104 - 26 under compressive strain is obtained by using a four-point bending method, which may inspire new possibilities for two-dimensional (2D) material-based microsystems and electronics.