The embodiment of the invention discloses an anti-fatigue-driving vehicle-mounted monitoring optical system. The anti-fatigue-driving vehicle-mounted monitoring optical system includes, in order froman object plane to an image plane along the optical axis, a first lens, a second lens, a third lens, and a fourth lens; an object side of the first lens is a convex surface, an image side of the firstlens is a concave surface, and the refractive power of the first lens is negative; an object side of the second lens is a convex surface, an image side of the second lens is a concave surface, and the refractive power of the second lens is positive; an object side of the third lens is a convex surface, an image side of the third lens is a convex surface, and the refractive power of the third lensis positive; and an object side of the fourth lens is a concave surface, an image side of the fourth lens is a convex surface, and the refractive power of the fourth lens is positive. On the other hand, the embodiment of the invention further provides a camera module. The optical system and the camera module of the embodiment of the invention are mainly composed of four lenses, the number of lenses is small, the structure is simple, the size is small, the weight is light, and the cost is low; the different lenses are combined with each other and the refractive power is reasonably distributed;and the anti-fatigue-driving vehicle-mounted monitoring optical system has good optical performance and can match a small anti-fatigue-driving vehicle-mounted monitoring system.