An optical imaging lens system comprising six lens elements (E1, E2, E3, E4, E5 and E6), the six lens elements (E1, E2, E3, E4, E5 and E6) being, in order from an object side to an image side along an optical path, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element, and each of the six lens elements (E1, E2, E3, E4, E5 and E6) having an object-side surface facing toward the object side and an image-side surface facing toward the image side; wherein a total number of lens elements in the optical imaging lens system is six, the first lens element has positive refractive power, the second lens element has positive refractive power, the image-side surface of the second lens element is convex in a paraxial region thereof, the object-side surface of the fourth lens element is concave in a paraxial region thereof, the image-side surface of the fourth lens element is convex in a paraxial region thereof, the image-side surface of the fifth lens element is convex in a paraxial region thereof, the sixth lens element has negative refractive power, the object-side surface of the sixth lens element is convex in a paraxial region thereof, the image-side surface of the sixth lens element is concave in a paraxial region thereof, and the image-side surface of the sixth lens element has at least one inflection point; wherein a focal length of the first lens element is f1, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, an axial distance between the first lens element and the second lens element is T12, an axial distance between the fifth lens element and the sixth lens element is T56, a curvature radius of the object-side surface of the fifth lens element is R9, a curvature radius of the image-side surface of the fifth lens element is R10, and the following conditions are satisfied: 0 ≤ f 1 / f 4 < 0.65; 0 ≤ f 5 / f 4 < 0.80; 0.70 < T 12 / T 56 < 6.50; and R 9 + R 10 / R 9 − R 10 < 2.50. wherein a total number of lens elements in the optical imaging lens system is six, the first lens element has positive refractive power, the second lens element has positive refractive power, the image-side surface of the second lens element is convex in a paraxial region thereof, the object-side surface of the fourth lens element is concave in a paraxial region thereof, the image-side surface of the fourth lens element is convex in a paraxial region thereof, the image-side surface of the fifth lens element is convex in a paraxial region thereof, the sixth lens element has negative refractive power, the object-side surface of the sixth lens element is convex in a paraxial region thereof, the image-side surface of the sixth lens element is concave in a paraxial region thereof, and the image-side surface of the sixth lens element has at least one inflection point; wherein a focal length of the first lens element is f1, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, an axial distance between the first lens element and the second lens element is T12, an axial distance between the fifth lens element and the sixth lens element is T56, a curvature radius of the object-side surface of the fifth lens element is R9, a curvature radius of the image-side surface of the fifth lens element is R10, and the following conditions are satisfied: 0 ≤ f 1 / f 4 < 0.65; 0 ≤ f 5 / f 4 < 0.80; 0.70 < T 12 / T 56 < 6.50; and R 9 + R 10 / R 9 − R 10 < 2.50.