Abstract: The practice on embankment of existing expressway shows that red sandy rock is not a good filling material of subgrade with relatively low natural strength. It is easy to crash and disintegrate, which leads to strength reduction, when it is exposed to atmospheric environment or under drying and watering cycle action. However, red sandy rock exists and distributes widely in our country, especially in areas where mountainous highways locate.Through a lot of experiments,the physical and mechanical properties and the performance of red sandy rock are discussed. Also, some disposal procedure and construction technique which should be adopted when red sandy rock is used as subgrade filling material are putted forward, the core of which is "pre-crack and decompose-rake and compress-grind and compress".