An optical fiber magnetic-field sensor based on Faraday effect using BiCaVIG crystal is developed and the configuration of its sensing element is described. The experimental results indicate that its dynamic range is better than 70 dB with the nonlinearity less than ±5% and its noise equivalent magnetic flux density is 1.5μT. The sensor can be used to measure pulsed magnetic field. By the method of frequency spectrum analysis, the dynamic response characteristics of a kind of BiCaVIG crystal is measured and its -3dB bandwidth is about DC～200 kHz.