The design method and fabrication process of 3rd overtone monolithic crystal filter have been studied in this paper. By optimizing the filter structure and reasonably controlling the frequency after wafer being evaporated, the high stop band suppression and high clutter suppression of the filter are realized. A monolithic crystal filter with operating frequency of 41.4 MHz and response mode of 3rd overtone has been fabricated. The experimental results show that the crystal filter has -1 dB bandwidth of 2.9 kHz, pass band ripple of 0.3 dB and stop band suppression of 82 dB.