Based on waveform records from the Xinjiang Regional Seismic Network，the paper analyses the spectral characteristics of foreshocks and aftershocks of February 12，2014 Yutian MS7． 3 earthquake sequence． We use genetic algorithm to invert source spectrum of 103 ML≥3． 0 events of the sequence． The results show that: (1) corner frequency of foreshocks is relatively lower than that of aftershocks; (2 ) using the nearest station’s ( YUT) data，we find that the observed spectrums of foreshocks are relatively independent of each other，the correlation coefficients of foreshocks and that of foreshocks to mainshock are on the low side; ( 3 ) the variation of correlation coefficients of observed spectrums implies dynamic rupture process of the earthquake sequence and most of the events with low correlation coefficients occurred on branch faults，which deviate from the main rupture area; (4) anomalously high frequencies of seismic radiation from foreshock sources are detected，which are probably due to an anomalous rigidity of the seismogenic medium． These features may be usable in foreshock discrimination．