To ensure the security of grain reserves and maintain the economic and social benefits related to agricultural products, the government should subsidize the agri-food supply chain members. At the same time, the agri-food supplier urgently needs live streaming to expand marketing channels. Based on this, this paper investigates the issue of strategy selection of the agri-food supply chain considering live-streaming under government subsidy. Thus, four scenarios are developed based on different combinations of situations where the choice of the target of government subsidies (agri-food supplier or streamer) and both parties in the supply chain enter into different agreements (commission or sharing). For this, the optimal decision of the government, agri-food supplier, and streamer in four situations are given, and the optimal strategies of all parties are compared and analysed. The theoretical results were verified through numerical experiments, and sensitivity analyses were conducted to identify further insights. The research conclusions are as follows. (i) The streamer is willing to pay more live-streaming effort for agricultural products with good fresh-keeping quality, and vice versa; (ii) If the government values the safety and freshness of agricultural products, the government should subsidize the agri-food supplier. In contrast, if the government focuses on the agricultural products' visibility, sales and popularity, the government should subsidize the streamer; (iii) In a given situation, there is the all-win strategy among all parties, i.e., the government subsidizes the agri-food supplier and the agri-food supplier enter into a sharing agreement with the streamer; (iv) The all-win region between the government and supply chain members will gradually shrinks with uncertainty increases. Overall, this research provides a theoretical basis for optimizing the supply chain system associated with live broadcast assistance to agriculture under government subsidies.