CaOMgOAl2O3SiO2 (CMAS) glassceramics were prepared by melting method using copper tailings as main raw material. The crystallization behavior of finegrained copper tailings based CMAS glassceramics was optimized by adding Fe2O3 crystal nucleation agent. The effect of nucleation agent content on the crystallization behavior and physical properties of finegrained copper tailings based CMAS glassceramics was studied by DSC, XRD and SEM, and the crystallization kinetics parameters were calculated by OzawaChen method. The results show that when the amount of Fe2O3 crystal nucleation agent is more than 3.72%(mass fraction), the glassceramics prepared from finegrained copper tailings can achieve overall crystallization. The precipitation of pyroxene phase is the result of coordination of Fe and Mg elements in glass phase into ［Si(Al)O4］ tetrahedral lattice. In addition, the increase of Fe3+ is conducive to the precipitation of pyroxene phase and reduces crystallization activation energy. The crystallization behavior and mechanical properties of finegrained copper tailings based glassceramics are optimized by Fe2O3 crystal nucleation agent.