This paper takes the crop system in the farmland as an example, applies the key information collection specification of crops, and formulates the key information collection specification through the research of collection index selection, sampling point layout, data collection method, data processing and other aspects. The farmland environment system based on the AHP-TOPSIS model guides the selection of field data collection points, the analysis of collection paths, and completes the collection of key data such as ground measurement and meteorology. The research results of this paper provide important data support for the establishment and verification of crop yield estimation models based on the combination of remote sensing and field data. The simulation results show that the maximum error between the predicted result and the actual value of the system is 2, which can effectively monitor the growth of crops.