A new multifunctional sensor (L1) based on phenylene-acetylene was designed and synthesized. L1 showed an excellently colorimetric response toward Fe2+ with a detection limit of 2.0☓10−8 M. This result indicated that L1 can sensitive detect Fe2+ by “naked eye” and discriminate iron types in different oxidative states. Simultaneously, L1 can ratiometric fluorescent detection of Cd2+ and Zn2+ with detection limits of 2.62☓10-8 M and 2.03☓10-9 M, respectively. L1 can distinguish Cd2+ and Zn2+ according to differently emissive colours, after addition of Cd2+ and Zn2+ to the blue emissive solution of L1, cyan and yellow-green fluorescence emission were observed, respectively. The binding modes of L1 with Fe2+, Cd2+ and Zn2+ were evidenced by 1H NMR, Job’s plot and ESI-MS. Water samples and On-site test paper experiments for detecting Fe2+, Cd2+ and Zn2+ were successfully implemented for practical application in environment.