Transition metal dichalcogenide (TMDC) monolayers exhibit enhanced electrical and optoelectrical properties, which are promising for next-generation optoelectronic devices. However, large-scale and uniform growth of TMDC monolayers with large grain size is still a considerable challenge. Presented in this work is a simple and effective approach to fabricating largescale molybdenum (MoS₂) disulfide monolayers by chemical vapor deposition (CVD) method. It is found that MoS₂ grows from single crystal into thin film with the increase of oxide precursor proportion. The photodetector of large scale monolayer layer MoS₂ film is fabricated by depositing metal electrodes on the interdigital electrode mask through using thermal evaporation coating. Finally, the highly stable and repeatable photoelectric responses under the conditions of different voltages and different laser power are characterized under 405-nm laser excitation, with response time decreasing down to the order of milliseconds (ms). In addition, the photodetector achieves a wide spectral detection range from 405 nm to 830 nm, that is, from visible light to near-infrared light wavelength range, with optical response (R) of 291.7 mA/W and optical detection rate (D^*) of 1.629×10⁹ Jones. The monolayer MoS₂ thin film photodetector demonstrated here has the advantages of low cost, feasibility of large-scale preparation, and good stability and repeatability in the wide spectrum range from visible light to near infrared light wavelength, providing the possibilities for future applications of electronic and optoelectronic devices .