The main purposes of this research are to develop the appropriate inventory of principals’ positive leadership in senior and vocational high schools, and to use the inventory to assess the current situation and differences of principals’ positive leadership in senior and vocational high schools. Firstly, a preliminary inventory is developed based on a review of the relevant literature, and the factor structure of the principals’ positive leadership inventory can be established after performing items analysis and the exploratory factor analysis. Secondly, 1,218 teachers from senior and vocational high schools in Taiwan are sampled for data analysis. For the further validation of the appropriateness on measurement model, through comparing the strategy of competing models, corrected factors model has been chosen as the measurement model for the principals’ positive leadership inventory. Then through the verifying methods of the individual item reliability, composite reliability, average variance extracted, convergent validity, discriminant validity and cross-validation, the reliability and validity of the model can be measured. Finally, according to the inventory that has been developed, to assess actual performance of principals’ positive leadership. This result shows that the principals’ positive leadership inventory contains four latent factors, including the guide of positive thinking and emotion, the use of communication knowledge and ability, the construction of interactive atmosphere, and the creation of positive meaning and value, and twenty four measurement items all together, which has good reliability and validity. In addition, the degree of principals’ positive leadership is at medium high level in senior and vocational high schools, and the teachers of different academic degrees, positions, school category have significant and different perceptions on principals’ positive leadership in senior and vocational high schools.