Based on the theory of the modified single-blow method, an automatic heat-transfer measuring system was designed and constructed to demonstrate the usefulness of the transient heat transfer testing method. New techniques were utilized in both air-heating and air-temperature measuring systems. A computer system was incorporated to calculate the temporally and spatially-averaged heat-transfer coefficient using the measured disturbance and response of the fluid temperature. The present system was applied to evaluate the heat-transfer performance of parallel-plate stacks and some other matrices of compact heat exchangers. The test results were compared with the existing theoretical and experimental data. It was confirmed that the present system has not only high accuracy (within ±5 percent) but also advantages of time-and labor-saving over conventional steady-state methods.