The role of the primary and secondary school mentor principal is to act as a guideline in a supportive role with the characteristics of a partnership to new and current principals, providing professional support to enhance school management knowledge and assisting in promoting local education policies. In addition, its candidates come from principals with rich school experience that have passed systematic training procedures. In order to cultivate mentor principal candidates effectively, to construct the mentor principal cultivation indicators (MPCIs) first before planning the training course may help principals to participate in training under the indicator system with objective and clear guidance. It also makes the training system conform to the mentor principals' career professional growth needs. The purpose of this article was to explain the use of MPCIs, then explore the issues that might arise while constructing MPCIs by contrasting the current training program in Taiwan. Finally, this article sorted out several strategies on how to construct MPCIs that correspond to the needs of career professional growth. A trial version of the cultivating indicator system was built as 2 stages. The first stage, "Master Training and Matching," is constructed with a total of 3 dimensions, 8 levels and 25 specific indicators. The second stage. "Master's Model and Inheritance," contains a total of 3 dimensions, 7 levels and 17 specific indicators. The indicator system may be provided for or follow-up academic research as well as to improve the current mentor principal training program in Taiwan. [ABSTRACT FROM AUTHOR]