Fiber optic rotary joint is used for signal transmission between stationary platform and rotary platform because of its advantages of high bandwidth,electromagnetic compatibility,small size,etc. A novel design of fiber optic rotary joint based on direct coupling technology of large mode area photonic crystal fiber(LMA-PCF)is designed. The analysis results of coupling theory indicate that this design provides low insertion loss and decrease requirement of accuracy of machining and assembly. Because LMA-PCF possesses the properties of non-cut-off-wavelength single-mode and lower non-linear transmission,the PCF optic rotary joint could be effectively associated with technology of WDM to increase transmission capacity.