The purpose of this study is to design a computational thinking curriculum standard for K-12 education. The Delphi technique was employed to collect different views and derive consensus from a panel of thirteen experts, including computer scientists, computer science educators, K-12 computer teachers, and industry experts. The first draft of Delphi survey questionnaire, consisting of nine themes (problem solving, problem decomposition, algorithms, data representation, data analysis, modeling and simulation, abstraction, automation, and others) and 60 competence indicators, was developed based on our investigation of the nature of computational thinking. After three rounds of survey and a final round-table discussion, the expert panel derived 49 essential competence indicators (13 for grades K to 6, nine for grades 7 to 9 and 27 of grades 10 to 12) and eight optional competence indicators (one for grades 7 to 9 and seven for grades 10 to 12). According to the results, the core ability and training of computational thinking are different in grades. In grades K to 6, students develop logical thinking and problem solving skills in personal and family life. In grades 7 to 9, students must understand the basic concepts of programming and write basic programs. Finally, in grades 10 to 12, they will use high-level skills to apply the concepts of abstraction, modeling, and structured problem decomposition to solve problems in different fields. The results serve as useful references for developing Taiwan's new K-12 computing curriculum.