Area-averaged fluxes measurement is widely used in fields of agriculture,meteorology and hydrology.Compared to tradition point measurements,optical device LAS (Large aperture scintillometer) is more accurate and reasonable for test of large natural areas.Based on the relationship between the refractive index structure parameter and the sensible heat flux,the LAS to measure the refractive index structure parameter and a software to calculate the sensible heat flux are devised.The scintillation strength measured by the LAS,together with the air temperature,wind speed and air pressure are processed by software to provide the sensible flux.The instrument consists of a transmitter,two receivers.It includes modulating,demodulating,filtering circuit,data acquisition,digital filtering,data processing and display parts.The experiment was performed in the summer of 2009 at Fengqiu Agro-ecological Experiment Station,in Henan Province.As a result,a good consistency is found between the sensible heat fluxes derived from LAS and the fluxes obtained from EC instrument.It proves that the scintillation method is a reliable technique.