This study has constructed a knowledge map of cross-disciplinary integrative STEM (Science, Technology, Engineering, and Mathematics) curriculum on robotic sailboat by using the webbed approach in the Cross-Disciplinary Thematic Integration Model. The thread method was used to display the linking relationships among relevant concepts on the map. Moreover, the Understanding by Design Model (UbD) was used to develop cross-disciplinary integrative STEM curriculum with robotic sailboat. Purposive sampling approach was adopted to select 42 first-grade students (35 males and 7 females) from one class in a senior high school. An instructor undertook task-oriented instruction and students undertook task-oriented hands-on activity. There were totally 21 teams with 2 members in each team via cooperative learning. Research results showed that students made significant progress on 7 fields of the test. Regarding skill performance, students made the highest performance on programming design; followed by sailboat design, mechanism assembling and installing, and significant level were reached in all activities. Attitude toward STEM showed significant improvement. Five significantly enhanced interests were engineering design, programming design, intention to study engineering or technology, intention to work in engineering field, and robotics. Three insignificantly enhanced interests were mathematics, science, and intention to work in mathematics or science field. The cross-disciplinary integrative STEM curriculum on robotic sailboat and the task-oriented instructional strategy might be the references for future development in integrative course and instruction of relevant themes.