Traditional post-harvest operation methods applied in rice fields lack advanced management knowledge and technology, which has led to post-harvest losses. We proposed the concept of Five Time (5T) management for the first time. 5T management divides the whole life cycle of rice into different growth time interval to complete process management. This paper mainly introduces the management of rice grain period, that is, the post-harvest management period, including the operation process management of harvesting, field stacking, drying, warehousing, and storing. In 2019, our research team formulated the 5T management method, which considers the entire post-harvest process, and carried out a pilot application of this method at the Jilin Rice Industry Alliance of Jilin Province. Moreover, to promote the 5T management method, our research team carried out follow-up experiments in rice production enterprises and found severe post-harvest rice losses. This paper combined a large number of literature and the basic theory research of rice post-harvest to analyze the traditional methods for post-harvest processing and the associated rice losses. By implementing the 5T management method, 4.33% of losses incurred during the T-1 harvesting period could be recovered. In the T-2 field period, drying rice within 48 h after harvesting could reduce losses by 2.5%. In the T-3 drying period, the loss rate could be reduced by 1.6% if traditional drying methods were replaced by mechanical drying and by 0.6% if cyclic drying was implemented to prevent over-drying. In the T-5 storage period, the loss rate of 7% could be reduced by adopting advanced grain storage technologies such as low-temperature storage. Overall, the rice loss rate could be reduced by 15.43%, which is equivalent to a yield of 32.68 million tonnes of rice. The important factors in each period are strictly controlled in the 5T management method to prevent the post-harvest losses caused by flawed concepts and improper management and to increase the amount of usable fertile land.