The invention provides a portable electronic device and an optical imaging lens thereof. The optical imaging lens comprises an aperture, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side in sequence, and meets the conditional expression: T4/G45<=2.8, wherein the T4 is the thickness of the fourth lens on an optical axis, and the G45 is air gap width between the fourth lens and the fifth lens on the optical axis. The invention also discloses the portable electronic device which comprises a housing and an image module arranged in the housing. The image module comprises the optical imaging lens above, a lens cone, a module back holder unit and an image sensor. The portable electronic device and the optical imaging lens thereof are used for photography; and through controlling the concave-convex face arrangement of each lens, the length of the lens is reduced under the condition of maintaining good optical performance.