Daguan County, in the Wumeng Mountains of Yunnan Province, Southwest China, is characterized by complex tectonics, steep terrain and highly seasonal rainfall, and is among the counties most severely affected by geological hazards in the province. This study applies distributed-scatterer time-series InSAR (DS-InSAR) to ascending and descending SAR imagery acquired between March 2024 and July 2026 by the L-band LuTan-1 (LT-1) constellation and by C-band Sentinel-1, deriving wide-area line-of-sight (LOS) velocity fields and deformation time series over a monitoring area of about 6.44 km around the county seat. Ascending–descending decomposition and singular spectrum analysis (SSA) separate the deformation at three deforming sites into trend, periodic and residual components, and cross-correlation, lag-response, cumulative regression and wavelet coherence analyses are used to test the temporal association between deformation and meteorological and other external variables. LT-1 shows a clear advantage in vegetated terrain: the ascending stack yields coherent points per km, a 23.74-fold density (2274.0% increase) relative to Sentinel-1 and a 42.22-fold density (4122.3%) within vegetated areas, while the descending stack yields points per km (10.55-fold, 954.6%; 22.87-fold, 2186.9% in vegetated areas). Because the two stacks also differ in incidence and azimuth angle, acquisition dates, repeat cycle and processing thresholds, this gain is reported as an operational advantage of the L-band mission rather than as an isolated wavelength effect. At significant-deformation points the two missions agree with correlation coefficients of 0.674 and 0.623 and root-mean-square errors of 15.32 and 2.72 mm/yr; this is moderate agreement, and the ascending comparison rests on only 49 matched pairs. Three clusters of significant deformation (H01–H03) were delineated for mm/yr. Two-dimensional decomposition indicates that the resolved motion is dominated by east–west horizontal displacement (mean rates of , and mm/yr, peak of mm/yr at H03), with horizontal-to-vertical trend ratios of 5.30, 1.79 and 4.16; because the north–south component is not resolved, these ratios describe an apparent horizontal dominance whose magnitude depends on the decomposition assumption. SSA reveals cumulative east–west trend displacements of mm at H01, mm at H02 and mm at H03, where the trend rate increases to mm/yr. At H03 the periodic amplitude of 30.46 mm reproduces most of the apparent rebound present in the raw series, so the rebound should not be read as stabilization; under the adopted decomposition it does not require a reversal of the trend. The east–west periodic component is associated with maximum air temperature (r = 0.364, 0.439 and 0.466) but only weakly with rainfall at zero lag. Following the M 3.9 earthquake of 12 December 2025, trend rates at H01 and H03 increased briefly, and the acceleration at H01 and H02 coincides in time with the period of most intensive urban construction; these coincidences are consistent with, but do not demonstrate, seismic and engineering triggering.