Abstract: The Cretaceous reservoirs in the western slope of Songliao basin mainly consists of delta and gravity flowdeposits, and the western slope area of Qingshantou formation before deposition is controlled by two grade slope break zones. In high slope break, the width is of 12~18 km and the gradient is of 0.7~0.8 degree. In the low slope break, the width is of 13~15 km and the gradient is of 1 degree. The west slope belt is controlled by high slope break at Yaojia formation, with the lower slope width of 13~16 km and the gradient of 0.4 degree. The relationship of the slope belt, source direction and sedimentary distribution was analyzed, and the result shows that the combination of high-lower slope break controls the distribution of reservoir types, and the source supply rate controls the scale of sand body. The gravity flow develops when the source direction is parallel to the slope direction, and the slope becomes transporting channel when vertical to source direction. The paleogeomorphology, the lacustrine level change and the source recharge are the main controlling factors of sedimentary development in western slope area of Songliao basin.