A lens assembly includes a first lens group, a second lens group, a third lens group, a fourth lens group, and a fifth lens group, all of which are arranged in order from a first side to a second side along an axis. The first lens group is with negative refractive power. The second lens group is with positive refractive power. The third lens group is with refractive power. The fourth lens group is with refractive power. The fifth lens group is with refractive power. The lens assembly further includes a first reflective element disposed between the first lens group and the fifth lens group, wherein the first reflective element includes a first reflective surface.