Determine several basic quantities and basic scientific concepts that reflect the state of the research object. This needs to be determined according to the existing scientific theories or hypotheses and the analysis of experimental information. For example, in the study of mechanical systems, the first physical quantities to be copied are mass principal quantity (M), velocity (V), acceleration (α), time (T), potential vector (R) and so on. It must be noted that the basic quantities to be determined should not be too many, otherwise there are too many unknowns and it is difficult to simplify them into possible mathematical models, so we must choose substantive and key physical quantities. Step 3: Grasp the principal contradiction and make scientific abstraction. The actual research object is complex, and many factors are mixed together. Therefore, it is very difficult to turn complex research objects into simple idealized research objects, and the key is to distinguish between primary and secondary. How to distinguish priorities can only be analyzed in detail, but there are also two basic principles: first, the mathematical model must be possible and at least an approximate solution can be given;