The 0.6 m continuous transonic wind tunnel of China Aerodynamics Research and Development Center （CARDC） is a circling wind tunnel using variable density dry air as working medium. Depending on the general performance calibration， the flow quality of the wind tunnel is tested in different conditions by parameters optimization of the walls （slotted or perforated）， acoustics treatments on the compressor tailor and the forth corner， re-adjusting the expansion angles of the test section walls and the re-entry slots， controlling the semi-flexible nozzle， the second throat and the plenum chamber pumping system. Testing results of the flow quality indicate that： The total pressure control precision in settling chamber is better than 0.1% and the Mach number control precision in test section is better than 0.001； The pressure fluctuating coefficient ΔC_p of the core flow in transonic test section is below 0.8%； The average flow deflection was better than 0.1°； Fluctuation of Mach number distribution and the standard model testing precision have met the requirements. The flow quality calibration demonstrated fully feasibility of the wind tunnel design scheme. The experience of 0.6 m wind tunnel provides a reference for the scheme design of China’s large continuous transonic wind tunnel and the quality assurance of international advanced flow field.