The lithium tantalite crystal was used as the piezoelectric material for crystal filter. Through optimizing the ion beam etching technique parameters, the micro crack in the etching area was overcome by using the interval ion beam etching technique, and the thickness of lithium tantalite wafer was thinned from 60 m to 30 m. A high fundamental frequency and wide band lithium tantalite crystal filter with center frequency of 70 MHz and 3 dB bandwidth of 1 109 kHz was fabricated by using the negative bench structure.