A new carbazole-based Zn2+ selective fluorescent sensor L has been developed. In CH3CN/H2O (1:1, v/v, HEPES 10 mM, pH=7.4) solution, L displays selective and ratiometric responses to Zn2+ through excimer formation. The Zn2+ recognition process has good anti-interference ability over other metal ions. The dinuclear complex Zn2L2 was further used as a receptor for oxalate. Through constructing a chemosensing ensemble with chromeazurol S, colorimetric recognition of oxalate in water solution was achieved via indicator displacement assays. The oxalate recognition process exhibits obvious color changes from blue to yellow and is naked eye detectable.