Two-dimensional semiconductor materials represented by MoS2 are one of the next-generation potential electronic materials that continue Moore's Law. However, the two-dimensional nature makes the transport behavior of electrons in MoS2 highly sensitive to environmental conditions. Encapsulation with van der Waals insulator materials is one of the effective solutions to eliminate the environmental sensitivity of two-dimentional semiconductor devices. In this paper, a novel van der Waals insulator material CrOCl was prepared by chemical vapor transport (CVT), and MoS2-based field effect transistors were designed and fabricated by using few-layer CrOCl as the dielectric layer and encapsulation material. The room temperature field effect mobility of MoS2 transistor with CrOCl as bottom gate dielectric layer and encapsulation material is about 60 cm2·V-1·s-1, which further increases to 100 cm2·V-1·s-1 at 2 K. In addition, compared with the hysteresis window of 20 V for unencapsulated MoS2 transistors, the protection of CrOCl effectively eliminates the hysteresis phenomenon of transistor transfer characteristics, proving its application potential in 2D material electronics.