A device for assembling a lens assembly includes a base, a barrel having a bottom, a universal joint disposed between the base and the bottom of the barrel, a push rod, and a resilient member. The universal joint is configured for allowing the barrel to tilt in any direction. The push rod is configured for depressing the lenses received to the barrel to form a lens barrel. The resilient member is disposed between the base and the bottom of the barrel. In process of assembling lenses, when the push rod presses the lenses received in the barrel, the lens assembly can hold the axis of the lenses in coaxial alignment under the cooperation of the universal joint and exert a uniformity force on a surface of the lenses. The lens assembly can eliminate the risk of breakage of the lenses and accurately position the lenses.