Leaf area index (LAI) is an important parameter for evaluating crop growth. It is also the main index to determine the spraying dosage of UAV. In order to establish a real-time measurement method of crop leaf area index (LAI), a rapid measurement system of winter wheat leaf area index was developed based on Android mobile platform. Under the condition of field, 10 evenly growing experimental areas were selected, and the canopy images of wheat were obtained by using the Android mobile platform and the ADC multi-spectral camera at different growth stages. Meanwhile, the actual leaves’ areas of wheat were artificially measured. According to the different measurement results, three kinds of leaf area index were calculated: (1) Converting Android mobile phone images from RGB to HSV, then calculating the green leaf area (IArea) after image segmentation on H-V dual channel combination image. (2) The leaf area index ALAI retrieved by the normalized vegetation index (NDVI) and the adjusted soil vegetation index (SAVI) data obtained by the ADC multi-spectral camera software. (3)The leaf area index (LAI) of actual manual measurement. With the different growth stages of wheat, the correlation analysis and modeling analysis of the above three leaf area indices showed that the R2 between the IArea obtained by the Android mobile platform and the actual measured leaf area index LAI was R2>0.84(P<0.01). And the R2 between the leaf area index ALAI obtained by the ADC and the actual measured leaf area index LAI was more than 0.83.