Practice has shown that polymer flooding has a good effect on improving oil recovery in the later stage of oilfield development. The accurate understanding of the residual economic recoverable reserves of polymer flooding is crucial for oilfield development decisions. However, the existing methods for calculating the residual economic recoverable reserves of polymer flooding use the cost of the polymer flooding stage from the beginning of polymer injection to the end of subsequent water drive, without considering the key link of the cost changes after turning to the subsequent water drive, lacks in consideration of different technical stages of the entire life cycle, resulting in major errors in calculating the economic recoverable reserves. In view of this, this study takes a single oil well as the core, starting from the different technical characteristics of the whole life cycle of the oil well, considering the variable cost at different stages, combining the production change law and the economic limit production model, deduces and establishes the fine calculation model of the remaining economic recoverable reserves of the polymer flooding. Taking the Block X of Placanticline Oilfield in Daqing as an example, the actual block was applied to the calculation, and the fine model was established to calculate the remaining economic recoverable reserves of polymer flooding as 2.27 × 104t, which increased the economic recoverable reserves of the whole life cycle by 0.82 × 104t compared with the calculation result of the previous method.