In this paper, a theoretical modeling analysis of LiNbO₃ integrated Y-waveguide based on a distributed polarization crosstalk analyzer was conducted using the Jones matrix and experimentally verified. Results of experiments show that the polarization crosstalk analyzer can evaluate the overall extinction ratio of Y-waveguide and test the crosstalk value of a defect inside the Y-waveguide, which compensates for the deficiency of the intensity extinction ratio tester. Finally, the rationality of test results of the Y-waveguide was verified by single polarization fiber. The distributed polarization crosstalk analyzer has great significance for screening LiNbO₃ integrated optical chips with better performance in practical applications.