An optical lens system includes nine lens elements which are, in order from an object side to an image side: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element, an eighth lens element and a ninth lens element. At least one lens surface of the seventh lens element, the eighth lens element and the ninth lens element has at least one critical point in an off-axis region thereof, and each of the seventh lens element, the eighth lens element and the ninth lens element has at least one lens surface being aspheric.