A lens module includes a holder, a connecting loop, engaging pins, an adjustment ring, a fixing pin; and a lens unit. The holder includes a barrel having a receiving space. The barrel defines sliding slots. The adjustment ring defines guiding grooves and a stopping slot. The connecting loop is received in the receiving space, the adjustment ring is sleeved over the barrel, and each engaging pin is secured with the connecting loop, an end of each engaging pin passing through a corresponding sliding slot and into a corresponding guiding groove. The fixing pin passes through the stopping slot and fixed with the barrel, the lens unit is secured with the connecting loop, the adjustment ring is rotated relative to the holder, and the engaging pin slides along the guiding groove, to cause the lens unit to axially move without rotating relative to the holder.