Based on the technologies of both object spectrum database and biological parametric models, the ground-object spectrum simulation signals were derived with the known LAI values. By use of computer simulation methods, effects of atmospheric condition and remote sensing detectors with assigned spectral sensitivity characteristics were simulated, and RS simulated signals on satellite level were produced. Furthermore, the performances of different sensors in detecting LAI were analyzed and compared, including CBERS-1, SPOT-1 HRV1, LANDSAT-5 TM and NOAA-14 AVHRR. Finally, on the criterion of LAI-detecting sensitivity, the paper designed and tested the best LAI-detecting band, and proposed the method of multiband remote sensing detector's parameter design based on digital simulated signal. The method has certain practical meanings in both the choices and optimums for sensor channels.