CBR is the key parameter to evaluate the load-carrying capacity of subgrade, which depends on many factors. By CBR tests on gravel-bearing sandstones of different particles, analyses the influence factors such as particle component, mineral component, immersion time and striking times, and analyses the prominent property of the above factors by means of nonrepeative double factors variance analysis. The results show that the compacted gravel-bearing sandstone after immerdion is difficult to be soften and has stable strength, which can be used to fill subgrade in southern heavy rainfall area, and the main influence factors of CBR is mineral component, immersion time and the compaction times, the impacts of particle size and dry density is relatively small. While it is difficult to improve the filling strength by increasing tamp power, increasing the content of coarse particles is a way to improve load-carrying capacity of subgrade.