Abstract: The pressure oscillation caused by condensation of unstable steam jet submerged in subcooled water was investigated experimentally. Results show that there are three typical flow patterns in the condensation process at different mass flow rates of steam jet and different temperatures of subcooled water, i.e. chugging (C), hemispherical bubble oscillation (HBO) and periodic bubble oscillation (PBO). The frequency of pressure oscillation increases with the rise of steam mass flow, which first increases and then decreases with rising temperature of subcooled water, and the maximum value appears in the transition area from chugging/HBO to PBO. The intensity of pressure oscillation in chugging/HBO region reduces and that in PBO region increases with the rise of steam mass flow. Moreover, the intensity of pressure oscillation increases with rising temperature of subcooled water under all the three flow patterns.