To better solve the problem of signal crosstalk caused by mode coupling in the transmission of few mode optical fiber, the transmission characteristics of linear polarization (LP) mode and vector mode in weakly coupled photonic crystal fibers were studied. A double clad photonic crystal fiber has been designed that can transmit 20 vector modes. The effect of fiber parameters on the minimum effective refractive index difference between adjacent LP modes was simulated using finite element method to optimize the structural parameters, allowing the fiber to support stable transmission of six LP modes, which meets the weak coupling requirements. Finally, the effective mode field area and bending loss of different modes were analyzed. The results show that the minimum refractive index difference between the modes of the fiber is more than 1.12×10^-4, indicating that the crosstalk between the modes is negligible. Effective mode field area of basic mode reaches 1040 μm², where the corresponding nonlinear coefficient is as low as 1.07×10^-10. In addition, at the bending radius of 38 mm, the maximum bending loss of each mode is only 5.65×10^-8 dB/km. Compared with mainstream single-mode fiber and few mode single cladding, this structure has larger mode field area, lower inter mode crosstalk and stronger bending resistance, enriching the development ideas of space division multiplexing technology. It provides useful reference solutions for emerging services such as big data, virtual reality, network transmission capacity and optical fiber sensing.