In the Weixinan sag, BBW basin, South China Sea, the laws of hydrocarbon migration and accumulation include the following basic characteristics: traps control the hydrocarbon distribution, reservoirs control the hydrocarbon accumulation, and the geophysical property of reservoirs and the property of fluids control the production capability. Therefore the development and distribution of various types of traps are very important for the hydrocarbon pool formation and distribution. Multiple structural traps as well as subtle traps develop in the Weixinan sag. In the Liushgang I Formation of lacustrine facies and multi-provenance, subtle traps of various types develop in two third-order sequences, including (fan)delta on steep slope, (fan) delta on gentle slope, basin fan, turbidite, sandbar formed from restructured delta front, onlap pinchout trap of lowstand sands. These nonstructural traps have good conditions of hydrocarbon migration and accumulation. Among these subtle trap types, (fan) deltas on gentle slope with stablesubsidence rates, small fan deltas on steep slope and highstand turbidites, which mainly locate in the mid-west part of the downthrown blocks of No.1 fault and No.2 fault, are easy to define and favorable for exploration.