Abstract: To recognize forming mechanism of source rocks in small-scale faulted lacustrine basins, the paper studies formation, distribution and geochemical characteristics of source rocks, and establishes 3 source rock formation patterns in small-scale faulted lacustrine basins by integrating the influences of organic matter supply, preservation and dilution on source rock forming. In a lacustrine basin with active boundary fault and high depositional rate, organic matter supply is sufficient but its preservation condition is poor, the source rock is mainly constrained by the organic matter supply and is mainly developed in deep depressions with abundant organic matter supply; in a lacustrine basin with inactive boundary fault and low depositional rate, the organic matter supply is of small quantity and its preservation condition is good, the source rock is mainly controlled by organic matter preservation conditions and is mostly distributed in gentle slopes with high reduction degree; in a lacustrine basin with moderate-active boundary fault and moderate depositional rate, the organic matter supply is of large quantity and its preservation condition is relatively good, the source rock is controlled by depositional rate, organic matter supply and preservation, and is developed in both deep depressions and near-depression gentle slopes.