Based on the initial freshness, the work aims to construct the order model to optimize the ordering strategy of fresh agricultural product retailers, combined with the fresh-keeping packaging input. In order to maximize the retailer's profit in a single sales cycle, the initial freshness was introduced into the perishable goods inventory model to build an order model for single-cycle fresh agricultural products in combination with the fresh-keeping packaging input. Then, the model was optimized with Matlab. The example showed that, when the sales cycle was 30 days, the fresh-keeping packaging input was 0.15 yuan and the initial freshness was 0.87, the maximum profit was 311.99 yuan; when the initial freshness rose from 0.6 to 0.95, the optimal order cycle rose from 2.86 to 23.66 days, the optimal order quantity rose from 74.76 kg to 120.60 kg, and then fell back to 101.37 kg; however, the maximum profit rose from 287.44 yuan to 327.13 yuan when the fresh-keeping packaging input rose from 0.05 yuan to 0.25 yuan; and the larger the initial freshness, the higher the margin of profit rose. It is found that, when the initial freshness is high, retailers can increase their profits by increasing the fresh-keeping packaging input and adopting the ordering strategy of less batches and more mass production; however, when the initial freshness is low, within the scope of food safety, retailers can increase their profits by reducing the fresh-keeping packaging input and adopting the method of more batches and less mass production.