BiY2Cr (x) Fe5-x O-12 (x = 0, 0.05, 0.1, 0.2, 0.3) nanocrystals were synthesized by using a sol-gel method. Samples were characterized by the powder X-ray diffraction (XRD), the thermal gravity analysis (TGA) and the differential thermal analysis (DTA), the vibrating sample magnetometer(VSM) and Mossbauer spectrums. The average sizes of the particles were determined by the Scherrer's formula. The special Ms and Mossbauer spectra of BiY2Cr (x) Fe5-x O-12 nanocrystals are researched at room temperature. It is seen that the special Mss of samples are initially increased with increasing Cr3+ content (x < 0.1), and decreased with increasing content of Cr3+ ions (x > 0.1).