In order to explore the exciton effect of two-dimensional layered transition metal sulfide, especially the up-conversion fluorescence process, the layered WS2 sample was taken as an example to study. Using 532 nm continuous laser and micro-Raman technology, the physical origin and basic properties of X0 and X- exciton of WS2 crystal were investigated. The continuous laser of 633 nm was used to realize single photon up-conversion fluorescence enhancement, which confirmed the physical mechanism of double resonance, that is, the incident light resonates with the X- exciton state, then exciton transitions to the high-energy X0 exciton state with the aid of optical phonons A1g and E12g, and finally produces spontaneous up-conversion fluorescence. In addition, the influencing factors of X0 were further analyzed including exposure time, temperature and excitation power. The fitting results showed that the up-conversion fluorescence efficiency could be improved by appropriately increasing the exposure time, decreasing the ambient temperature and increasing the excitation power.