Bulk amorphous Cu52.5Ti30Zr11.5Ni6(at.%) alloys up to 5 mm in diameter were fabricated by a copper mold casting method.The critical cooling rate was determined to be 126.8 K/s by using the Barandiaran-Colmenero expression.Based upon the Jackson-Hunt relation,the cooling rate for the formation of devitrified structure was also evaluated.In the cooling range of 10 K/s ~ 120 K/s,there exists a mixed microstructure of primary metastable phase and eutectic structure.With further decreasing of cooling rate(below 10K/s),the precipitation of metastable phase was depressed,and the growth mode also deviates from the eutectic mode.