This paper deals with the ultrasonic degradation of tetracycline hydrochloride （TC.HCl） in aqueous solution and reveals the effects of ultrasonic frequency, ultrasonic power, initial mass concentration of the solution, pH value and anion on the degradation efficiency. The results indicate that （1） with ultrasonic irradiation, TC . HCl in aqueous solution effectively degrades with high speed, which accords with the pseudo first-order reaction model; （2） at a pH value of about 5.60, 88. 17% of 1.00mg/L TC . HCl is decomposed within 20min under the irradiation with 400 kHz and 100 W ultrasonic ; （3） the degradation rate of TC . HCl increases with the increase in ultrasonic power and with the decrease in the initial TC . HCl concentration; （4） the pH value of the solution greatly influences the TC . HCl degradation and the degradation performs well in alkaline condition; and （5） Cl^- and SO₄ ^2- slightly inhibit the degradation, while NO₃^- , HCO₃^-、 and HPO₄ ^2- accelerate the degradation, especially the latter two.