Based on four-wave mixing in highly nonlinear fiber, a scheme to chaotic laser sampling independent of polarization is proposed due to poor coherence of chaotic laser, and random fluctuations of polarization state. And the chaotic laser with wavelength of 1550 nm and power range from 0~10 mW is sampled by numerical method. It can be found that the four-wave mixing sampling can be optimal for the pump light with wavelength of 1557 nm and power of 2 W when the fiber length is 60 m. Using the above parameters, polarization insensitive sampling for chaotic laser is implemented with sample rate of 5 GHz. The peak power of the chaotic pulse is amplified. The gain coefficient is approximately 10.8 dB. The results can provide a theoretical basis for the further experiment.