A driving assist system executes risk avoidance control for reducing a risk of collision with a target existing ahead of a vehicle. A vehicle state parameter includes imaginary relative position and velocity of the vehicle. A target state parameter includes expected direction and speed of movement the target. A risk value is expressed by a function of an estimated collision speed between the vehicle defined by the vehicle state parameter and the target defined by the target state parameter. The driving assist system sets multiple patterns of the target state parameter and sets a probability of each target state parameter. A partial risk value is the risk value when each target state parameter is used. A final risk value applied to the risk avoidance control is a sum of products of the probability and the partial risk value with respect to the multiple patterns of target state parameter.