A lens arrangement includes two lenses. Each lens includes an optical portion having an optical axis, a non-optical portion surrounding the optical portion, and an engagement portion extending along the optical axis from the non-optical portion. One of the engagement portions includes an outer wall and an inner wall parallel to the outer wall with an annular groove defined therebetween, while the other engagement portion defines a corresponding annular space for receiving the outer wall and the inner wall therein, therefore the engagement portions are interferentially engaged with each other.