Abstract: In order to solve the processing problems of the test article occurred in the cascade experimental research, investigation and study of the processing technologies of the test blade and Aero-Plexiglass sidewall have been carried out through processing test and experimental validation. And then the detection methods of the key parameters are put forward based on trilinear coordinates measuring instrument. It can be seen from the results that considering the processing cost and the effects of the blade surface roughness on the cascade performance, the suitable surface roughness of the blade for high speed and high load cascade is suggested to be not more than Ra=1.6. Stress lines and black areas may appear on the Aero-Plexiglass sidewall due to some factors, such as material selections, manufacturing procedures, processing technologies and improper assembly or use, etc., which would cause adverse effect on schlieren visual measurement in high speed state. The processing quality of the test article is greatly improved by developing the detection methods of the key parameters, which will be helpful to get more accurate and reliable performance data.