In this paper, the wrinkling and failure behavior of single layer MoS2 (SLMoS2) sheets under in-plane shear is investigated using molecular simulations and the nonlocal model. Wrinkling and failure features, such as the stress-strain relation, the amplitude and the half-wavelength, are comprehensively explored. The effects of size, temperature and pre-existing cracks on the wrinkling and failure behavior are then taken into consideration. It is found that the whole process can be divided into three stages, i.e., the pre-buckling stage, the buckling stage and the failure stage. The classical continuum model is found to be limited in quantitatively analyzing the wrinkling behavior due to the lack of size effect. The nonlocal parameter, a key parameter to characterize the size effect, is first reported. What is more, compared with edge cracks, SLMoS2 sheets are more sensitive to pre-existing centre cracks. This work can provide a better understanding of the wrinkling and failure properties of SLMoS2 sheets under shear loads, and should be helpful for developing various flexible electronic devices.