For frequencyvarying vibration signals from rotary machineries, the order tracking analysis method can avoid the frequency aliasing phenomenon in th e FFT analysis. Presently the sampling frequency in time domain is determined by experiences in the experiments and order aliasing exists during resampling in angular domain. This paper described the relationship of the time domain samplin g and angular domain resampling, and the analysis band of angular domain and t i me domain sampling frequency of anticipative rotational speed were obtained. Acc ording to the sampling frequency and the actual rotational speed, the order of a ngular domain resampling and the analytical band were determined. Then the con d ition was deduced that time domain sampling frequency and order sampling must be satisfied, and a simulation example was analyzed. At last, the vibration signal analysis of an aeroengine shows that the above conclusion is effective.