According to the shortcomings of general method such as nonstandard operation and big test errors, a testing method based on intermittent non-steady state method was put forward to evaluate the standard oxygen transfer rate of the oxygenator. The paper introduced the facilities needed for the test, the testing step and the calculation method in detail. Using this method, DP18-Y, a multi-stage trickling oxygenator was tested. With two different G/L ratios 1:100 and 1.5:100, after about 130 min and 220 min running period separately, dissolved oxygen concentration (DO) in the testing pool had reached 17 mg/L, standard deviations at three DO probe positions were less than ±0.78. To verify the repeatability of the method, the test was repeated three times with the two G/L ratios, and the standard oxygen transfer rate calculated as a result was (206.1±5.7) kg/h and (248.5±11.3) kg/h, respectively. Calculated by different ranges, it was found that the calculation result would be more precision with the start point closer to 0 mg/L and the end point over 70% of theoretical DO saturation concentration. The results show that the method has good stability and repeatability and is feasible to evaluate the oxygen transfer rate of any oxygenator.