Abstract: By installing grain yield monitoring system in wheeled harvester，data records could be provided to farmers for farm management，and agronomic，remote sensing，weather and soil data could be combined to provide data support for variable operation，so as to realize smart agriculture.Basic principle of grain yield monitoring system was introduced，calibration and debugging tests were carried out，and finally field measurement was carried out.Results showed that error between monitoring system and actual measurement data was-3.3%，which could meet actual production requirements.Grain yield monitoring system is beneficial to reduce input of pesticides and fertilizers，improve grain yield and quality，and ensure food security.