To improve the precision of electro-hydraulic servo valve’s dynamic state character, a method was proposed by having the excitation signal integrated while calculated the servo valve’s frequency characteristic. In the measurement system, a programmable logic controller (PLC) controlled the cylinder’s displacement with a low frequency, while a displacement sensor detected the response signal with a high frequency, which would reduce the inherent error. The rest automatic operations were completed in the national instruments’ products (PXIe-1071, PXIe-8115 and PXIe-6251). In the software program, a LabVIEW produced control signal with a fixed value of sample and a change frequency, was sent to the PLC system, which would produce the final excitation signal. The valve’s displacement could be got, and the integration of the final excitation signal and the valve’s displacement signal were calculated. Finally, the servo valve’s dynamic state character could be got. At last, the MOOG D761-2716A servo valve’s test curve and the MOOG D661-1945E servo valve’s test curve were illustrated, which meet the correct results well. In the end, several conclusions were drawn: the method of having the excitation signal integrated can be used in the test of electrohydraulic servo valve and it can calculate the dynamic state value accurately. The composite measurement system (PLC+NI) can play a correct role in the test.