Abstract: To accurately understand the dynamic change patterns of the injection system Ji Di (JD) medium molecular weight salt-resistant polymer prepared in fresh water and diluted in produced water, the application effect of JD medium molecular weight salt-resistant polymer was evaluated by comparing it with other blocks that inject different systems within the same stratigraphic series. A preliminary study was conducted on the dynamic changes and effectiveness characteristics at both injection and production ends. It was concluded that the JD medium molecular weight salt-resistant polymer shows good adaptability to the oil layers in the JY block and exhibits better polymer flooding effects in the early and middle stages than other salt-resistant polymers. It is determined that the JD medium molecular weight salt-resistant polymer is characterized by a significant pressure increase during the initial injection stage, low injection concentration and injection rate, and a large decrease in injection-production capacity. These characteristics indicate that the JD medium molecular weight salt-resistant polymer has good profile control and plugging capabilities, making it suitable for low-concentration and low-rate injection methods. Moreover, compared with other blocks within the same stratigraphic series, under the same enhanced oil recovery (EOR) conditions, JD medium molecular weight salt-resistant polymer requires a lower polymer dosage. At the production end, it shows earlier response time, faster water cut decline, larger decline amplitude, longer stable period of low water cut, and relatively better water cut reduction and oil increment effects. Due to the strong profile control and plugging effect of JD medium-molecular-weight salt-resistant polymer, it has a significant impact on the injection-production capacity of the block. Therefore, it is necessary to formulate adjustment strategies based on the dynamic variation law at both the injection and production ends to improve the block development effect and enhance economic benefits.