Using Schuster statistical test method, the correlation between tidal body stress and moderate and small earthquakes occurred in the epicenter and its vicinity before the Xizang Dingri M_S6.8 earthquake on January 7, 2025 is investigated. The test results were evaluated by the statistical parameter P value, and the lower the P value, the stronger the statistical significance of the correlation. According to the phase angle statistics of the tidal force modulation caused by the semidiurnal tide and the semilunar tide in the epicenter, the P value of the semidiurnal tide test result is 1.26%, which is lower than triggering threshold of the tidal stress, and most earthquakes occur near the minimum of the semidiurnal tide; the P value of the semilunar tide does not pass the significance test. Further analysis of the temporal and spatial smoothing windows of the P-value based on the semidiurnal tide shows that the P-value decreases significantly before the Dingri M_S6.8 earthquake, and the low P-value area of the spatial smoothing window is concentrated in the north of the epicenter of the Dingri M_S6.8 earthquake. It is shown that the occurrence of moderate and small earthquakes in the epicenter and its vicinity before the Dingri M_S6.8 earthquake is obviously related to the triggering of solid tide, and these moderate and small earthquakes have certain precursory significance for the occurrence of the Dingri M_S6.8 earthquake.