The paper described how to realize the small cross-coupled cavity filter by HFSS，designed a four-cavity filter,which material was copper, center frequency was 0.945GHz,passband was 30MHz,S21 was lower than -20dB at the frequency point of 10MHz higher and lower than passband, S21 was higher than -0.5dB and S11 was lower than -10dB in the passband.The filter size is 90mm*90mm*35mm,which achieve a better band edge suppression without increasing the number of the cavities and is adjustable,compare with the filter that has the same performance it is much more smaller.