The nonisothermal crystallization kinetic of BixY3-xFe5O12 (0.25 <= x <= 1.00) powders prepared by coprecipitation process has been investigated. The activation energy of crystallization was calculated by differential scanning calorimetry at different heating rates. The activation energies of crystallization of BixY3-xFe5O12 system are 492, 447, 377, and 353 kJ/mol and the Avrami constant n are 3.49, 2.25, 2.48, and 2.33 for x=0.25, 0.50, 0.75, and 1.00, respectively. The Avrami exponent values (1 < n < 3) were consistent with surface and internal crystallizations occurring simultaneously for 0.50 <= x <= 1.00, the value (n > 3) for the Avrami exponent was consistent with bulk crystallization domination in BixY3-xFe5O12 system. The results reveal that increasing the substitution amount of bismuth for yttrium would significantly decrease activation energy in BixY3-xFe5O12 system.