In the replacement from old version to new version, there is a conflict between the new double “H” silicon resonant pressure sensor and the traditional pressure sensor, such as vibration cylinder and single beam silicon resonant. To solve the problem, develops a dual-frequency acquisition and synthesis system, which is based on the GD32 single-chip timer counting and interrupt timing technology. The system builds a multiple timer synchronous counting circuit by using the tiny single-chip microcomputer ( GD32F405RGT6) to realize dual frequency 20 ms synchronous acquisition. On this basis, a new digital frequency conversion method is proposed, which can control the I/ O port flipping level by the timer interrupt of the single-chip microcomputer to outputs square wave. And a dual-frequency synthesis error compensation method is designed to decrease the maximum theoretical error of the dual-frequency synthesis from 51. 15 Pa to 0. 127 9 Pa. Experimental results show that the system can work under -45℃ ~ +85℃ and 2~ 266 kPa. The single frequency range of the system output is 4~ 10 kHz. The dual frequency acquisition and synthesis error is less than 0. 005% of the full pressure scale. The digital circuit board is small and can be integrated into the new double “H” type silicon resonant pressure sensor circuit, which well satisfies the requirement of the dual frequency acquisition and synthesis output for the silicon resonant pressure sensor in atmospheric pressure detection and monitoring.