The relaxation oscillation characteristics of a resonant tunneling diode (RTD) with applied pressure are reported. The oscillation circuit is simulated and designed by Pspice 8. 0, and the measured oscillation frequency is up to 200kHz. Using molecular beam epitaxy (MBE) ,AIAs/lnx Ga1-x As/GaAs double barrier resonant tunneling structures (DBRTS) are grown on (100) semi-insulated (SI) GaAs substrate,and the RTD is processed by Au/Ge/Ni/Au metallization and an airbridge structure. Because of the piezoresistive effect of RTD,with Raman spectrum to measure the applied pressure, the relaxation oscillation characteristics have been studied, which show that the relaxation oscillation frequency has approxi- mately a - 17.9kHz/MPa change.