Ras is a kind of protein closely related to neoplasms,the persistent activation of which would induce tumorigenesis and progression.RASAL1 is a Ca~(2+) regulated ras GTPase-activating-like protein, the loss or decreased expression of RASAL1 induces ras activation, then results in tumongenesis and progression.In this review we sum up the mechanism of ras activation, the relationship between neoplasms and RASAL1 and the mechanism of RASAL1 expression decreasing.