Terahertz wave has unique advantages in nondestructive testing and safety monitoring because of its special spectral position, penetration, low energy, sensitivity to polar molecules and friendliness to nonpolar materials. In this experiment, terahertz time-domain spectroscopic imaging system is utilized to image tridacna samples with slot defects by changing the polarization direction of incidence and detection. Due to the low transmittance and large dispersion of the tridacna material, the traditional direct imaging results cannot be distinguished, and it is difficult to achieve the desired results. The polarization imaging results are reprocessed by introducing the concept of Jones vector and Jones matrix. The results show that this method is very sensitive to the edge information of the defect and can effectively improve the resolution of the imaging results of the tridacna material.