To measure party positions should be a theory-guided empirical research, even though it is only about to measure a variable. This research starts with explaining why approach and theories are important to the selection of variables and how to measure them. Secondly, the content analysis developed by Manifesto Research Group (MRG) and a variety of obtrusive methods of measurements are introduced, including what they are and their advantages and disadvantages. Thirdly, the Taiwanese parties’ positions on Taiwan Independence, Left-Right Dimension, and Environmental Protection and Economy Growth are measured by the MRG methods with party manifestos and electoral gazettes. Besides, expert surveys and mass surveys are used as a supplement. The measures from content analysis are compared with that from surveys in order to assure the validity of the data. The results show that party positions measured by content analysis and surveys are similar. Therefore, because of its solid theory, public and replicable coding procedure, and acceptable reliability and validity, the method of measuring party positions developed by MRG provides quality data of party positions.