Hydrocarbon accumulation process and oil-bearing property controlling factors of lithological reservoir were observed and modeled by NMR (nuclear magnetic resonance) experimental modeling. The experimental results showed that the hydrocarbon accumulation process is slow and hydrocarbon migration has upward, downward and lateral directions. Migration speed is much greater in the former direction than the latter two, and temperature, pressure, reservoir property of sandbody, and oil-bearing property of surrounding mudstone play important roles on the oil-bearing property of sandbody. Based on NMR experiments, micro-hydrocarbon accumulation mechanism of lithological reservoir was analyzed and three stages of accumulation process were presented, that is, the first stage is the migration process along kerogen organic networks in the middle of pores of mudstone by diffusion and hydrocarbon concentrate difference pressure as drive and capillary pressure as resistance, the second stage is the filtering process in the interface of sandstone and mudstone pores and throats by capillary pressure difference, and the third stage is hydrocarbon filling process in sandstone by buoyancy conquering liquid flowing sticky and adsorbing resistance forces.