Pressure oscillation may be induced in liquid when steam is injected into subcooled liquid through a submerged pipe. Theoretical and experimental considerations have been made on mechanism of the pressure oscillation in the case that an oscillatory condensation interface exists at the pipe exit. The pressure oscillation is triggered by a physical process in a vapor phase, being strongly affected by the type of condensation heat transfer at the vapor-liquid interface. A heat-transfer mechanism proposed here well explains parametric effects on various characteristics of the pressure oscillation. A new dimensionless parameter of subcooling is proposed which correlatees water and freon data better than Jacob number. Operational ranges for the onset of pressure oscillation as well as its frequency and amplitude are obtained in analytical forms which are verified by experiments in a wide range of parameters.