Abstract: Addressing the core problems in NC programming and process experimental teaching—insufficient equipment, invisible cutting process, delayed error exposure, and evaluation biased toward terminal results—this paper proposes an experimental teaching mechanism under the concept of “navigation surgery”. On the basis of analyzing the difficulties of the traditional “programming—machining” linear model, and taking the NC milling experiment of a complex curved valve-cover part as an example, the practical paths in preoperative planning, simulation navigation, precise implementation and postoperative evaluation are elaborated. Through mechanism innovation, the course achieved a series of outcomes in moving the exposure of problems to earlier stages, strengthening process planning competence, standardizing process evaluation and improving task quality: the error interception rate in the simulation stage reached 85.6%, the average number of machine-tool rework operations per group decreased from 2.3 to 0.6, the average machine occupation time per group decreased from 58.4 min to 36.2 min, the task qualification rate rose from 72% to 93%, and the excellence rate of comprehensive experiment reports increased from 62% to 83%; the mechanism also promoted a sustainable transition of NC experimental teaching from operation-oriented training to precision machining training for complex tasks. The proposed mechanism can provide a practical reference for the reform of NC milling experiments for complex parts.