Aiming at the temperature stability of the hydrophone, this paper studies the change law of the sensitivity of a piezoelectric circular tube hydrophone when the ambient temperature changes. The main influencing factors of temperature on the hydrophone are analyzed through the calculation formula of the free-field voltage receiving sensitivity of the circular tube hydrophone at low frequency, and the variation law of the hydrophone sensitivity with temperature is analyzed and calculated based on the thermodynamic theory. The change of the capacitance of a cylindrical piezoelectric ceramic with temperature, and the change of capacitance and sensitivity of the piezoelectric ceramic with different coating materials with temperature were measured, and the difference between the measured values and the theoretical values was compared and analyzed. The results show that the sensitivity of the hydrophone is negatively correlated with the temperature, and the capacitance of the hydrophone is positively correlated with the temperature, which is consistent with the theoretical analysis. The difference between the theoretical value and the measured value is mainly caused by the thermal expansion characteristics of the hydrophone surface coating material itself and the temperature characteristics of the acoustic impedance.