A new C-3-symmetric Schiff-base fluorescent probe (L) based on 8-hydroxy-2-methylquinoline has been developed. As expected, the probe L can display high fluorescent selectivity for Cd2+ over Zn-2+ and most other common ions in neutral ethanol aqueous medium. Moreover, the mechanism of the LCd2+ complex has been confirmed by X-ray crystallography and density functional theory calculation results. More importantly, L could be used to image Cd2+ within living cells.