At present

optical remote sensing is the primary way to retrieve vegetation Leaf Area Index（LAI）.However

certainproblems

such as optical radiation saturation

cause low LAI reversion accuracy

especially when the LAI is large.The LAI and average leaf inclination angle are important factors affecting the reflecting and scattering characteristics of the canopy in the optical and microwave regions.Microwave remote sensing data has the potential to aid LAI retrieval to improve the problem of saturation in the optical region.In this paper

maize is used as a model system to analyze the feasibility of this method.The input parameters of PROSAIL and MIMICS were analyzed

and a unified model scene was constructed by unifying the parameters of the two models.Based on the coupled PROSAIL and MIMICS model

the parameter sensitivity analysis was conducted

and two vegetation i ndices that are more sensitive to LAI were proposed:MNDVI（800 nm

2000 nm） in the optical bands

and SAR SRVI（1.4 GHz HH

9.6 GHz HV） in the microwave bands.The two vegetation indices are sensitive to different LAI levels.The optical vegetation index

M NDVI（800 nm

2000 nm）

is sensitive to LAI ranging from 0 to 3.The RMSE and R2of the regression model are 0.33 and 0.958

r espectively

when the step of LAI change is 0.4.The microwave vegetation index

SARSRVI（1.4 GHz

9.6 GHz）

is sensitive to LAI ranging from 3 to 6.The RMSE and R2are 0.22 and 0.984

respectively

when the step of LAI change is 1.Based on our results

we c onclude that it is feasible to retrieve the LAI by piecewise vegetation indices of MNDVI（800 nm

2000 nm） and SARSRVI（1.4 GHz HH

9.6 GHz HV） to couple the advantages of the optical and microwave bands.