Abstract: The presence of high-helium shows in natural gas from the Northern Songliao Basin indicates significant helium resource potential. However, compared to the southern part, the spatial distribution patterns of helium remain unclear, the genetic mechanism of crust-derived helium is uncertain, and systematic analysis of fault-caprock coupling control on accumulation is lacking, which constrains exploration deployment. This study is based on high-precision helium isotope data （R/Ra = 0.04-1.86） from 53 natural gas samples （depth: 455.4-3 935 m）. The R/Ra ratio method is employed to quantitatively determine gas sources, integrating structural zoning, fault geometric parameters, caprock properties, and magmatic activity for coupling analysis. The results demonstrate that: ①helium accumulation is characterized by crust-dominated, crust-mantle mixed sources, with crustal helium contributing an average of ＞75% （mean R/Ra = 0.92） from radioactive decay in basement granitic rocks; mantle-derived helium accounts for ＜25%, limited by the transport efficiency of low-angle basement faults （dip angle ＜30°）, with flux only 50% of the southern basin. ②A slope k＞0.3 from the intersection of mantle-derived helium versus total helium content is proposed for the first time as the threshold for efficient transport, quantitatively revealing the low-angle fault control mechanism. ③High-quality mudstone caprocks of the Qingshankou-Nenjiang Formations are crucial for helium preservation, with shallow helium content （740 μL/L） showing a 174% increase compared to deep layers （270 μL/L）. ④Magma-fault coupling enhances fracture permeability by 10²-10³ times, significantly promoting mantle-derived helium enrichment. ⑤A dual accumulation model is established: “static accumulation of crust-derived helium” and “fault-dominated enrichment of mantle-derived helium”, clarifying that the north-south difference stems from deep transport system efficiency variations. This study systematically reveals helium enrichment mechanisms in the Northern Songliao Basin, innovatively proposing low-angle fault control and dynamic coupling enrichment models, providing important reference for local target optimization and helium exploration in similar basins in China.