The invention provides a new method for calculating the production through an indicator diagram of a heavy oil well. The new method comprises the steps that 1, the indicator diagram is decomposed intoa plurality of load points according to horizontal coordinates; 2, the load points are projected to a longitudinal axis; 3, the load range where an effective stroke section is located is determined according to the density of the load points on the longitudinal axis, and if one or more sections of discontinuous load ranges are screened, the load range section with the minimum mean load is selected as the load range where the effective stroke section is located; 4, within the determined load range, the load point with the maximum displacement is connected with the load point with the minimum displacement, and a connecting line of the two points is the effective stroke section; and 5, the length of the effective stroke section is calculated and substituted into a computational formula of aneffective stroke method, and the single-well daily fluid production rate is calculated. According to the new method, the problem of calculating the production of heavy oil, especially ultra-thick oilthrough the indicator diagram is solved, the calculation accuracy is high, and compared with an existing indicator diagram computer production calculation method, the selected effective stroke section is higher in accuracy and higher in universality.