Discrete-time and continuous-time modeling methods for refining process scheduling have limitations in application. In view of this, this paper proposes an instant delivery based discrete-time modeling method. This method generally adopts discrete time representation. Through more detailed description of the relevant parts of the product delivery, the delivery activities can occur within the time interval, which not only ensures accurate description of actual problems, but also achieves effective control of the model scale. Taking the modification and blending process of a refinery in North China as an example, a discrete-time model, a continuous-time model, and an instant delivery based discrete-time model are established, respectively. According to the solution to the three cases, the three models are compared from different perspectives. The research results show that the model proposed in this paper has both the advantages of the original discrete-time model and continuous-time model, and can maintain stable and good performance in different situations.