Assessing the contribution made by new seed cultivars to nationwide yield increases is critically important to planning for future yields. This study focuses on a method that enables the contribution of seed cultivars to nationwide yield increases to be estimated by means of dividing the study period into several diffusion periods characterised by the replacement of major seed cultivars and by specifying a yield response model that incorporates a series of dummy variables to capture net increases due to new cultivar diffusion in each such period. Using this method, the contributions over the base period were estimated to be 1303.8 kg/ha, 523.0 kg/ha, 1179.5 kg/ha, 316.9 kg/ha, 196.8 kg/ha, and 414.2 kg/ha for rice, wheat, corn, soybeans, cotton, and rapeseed, respectively, accounting for 47.9%, 33.3%, 47.6%, 41.4%, 34.0%, and 46.5% of total yield increases, respectively. This method has several advantages, being concise, easy to use, and flexible; further, it can distinguish historical contributions of seed and can therefore be used for tracking assessments. It is thus likely to be applicable in several practical ways to measure the developmental status of both seed breeding technologies and agricultural techniques. Acknowledgement : This research is financially supported by the Agricultural Science and Technology Innovation Program (ASTIP-IAED-2017-05), the Project Sponsored by the Ministry of Agriculture of the People s Republic of China (11162130109236061), and the Project Sponsored by the Basic Research Foundation for the Central Public Institutes (Y2016ZK20)