The invention provides a thermal power unit pure-condensing working condition sliding pressure curve determination method with valve throttling loss being taken into consideration and relates to a thermal power unit pure-condensing working condition sliding pressure curve determination method, and is to solve the problems of complex sliding pressure experiment data obtaining process, inaccuracy of a sliding pressure curve obtained through a sliding pressure experiment and high thermal loss of a thermal power unit in an existing sliding pressure curve determination method. The method comprises the following steps: 1) collecting overall working condition historical data in a unit DCS system; 2) screening the data in the step 1), and carrying out grouping statistics on the data in a load interval to be collected; 3) carrying out data analysis on the data in each load interval to obtain optimal main steam pressure corresponding to corresponding load points; and 4) obtaining a sliding pressure curve by utilizing the optimal main steam pressure of each load point obtained in the step 3). The method is used in steam turbine operation.