To improve the rationality in river longitudinal connectivity evaluation, an enhanced barrier coefficient method was proposed based on the traditional barrier coefficient method, which takes into account the location and type of river blocking structures by introducing corresponding correction factors. The enhanced barrier coefficient method was used to assess the longitudinal connectivity for 215 major rivers across China, each with a watershed area exceeding 10 thousand km². The results indicate that in 2020, the average longitudinal connectivity index of the evaluated rivers was 1.08, categorized as a poor level. Temporally, since 1960, the longitudinal connectivity of the major rivers has exhibited an accelerating trend of deterioration, with the most intense deterioration occurring after 2000. Spatially, the worst longitudinal connectivity occurred in the Southeast River Region, Pearl River Basin, and Yangtze River Basin, categorized as a very poor level, the Haihe River Basin and Liaohe River Basin were categorized as a poor level in the longitudinal connectivity, and the Songhuajiang River Basin was the sole area exhibiting the best connectivity.