In Article 335 of China's Criminal Law regarding the crime of medical accident, the interpretation of "serious dereliction of duty" directly affects the determination of criminal medical negligence. However, issues such as insufficient normative supply and vague judicial determination have led to frequent occurrences of inconsistent judgments in similar cases. Among existing theories, the "subjective theory," "objective theory," and "comprehensive theory" all have deficiencies. Accordingly, we should re-examine the interpretive logic of "serious dereliction of duty," adopt "gross negligence" as the interpretive dimension, and construct a new comprehensive theory. This theory defines "serious dereliction of duty" as a composite subjective-objective element, requiring simultaneous satisfaction of the standards of "ease and inadequacy in fulfilling the duty of foresight" and "high degree of foreseeability." The new comprehensive theory not only provides doctrinal guidance for the normative application of the crime of medical accident but also, through verification with the Li Mouxue case and the Luo Moumou case, demonstrates its practical value in clarifying the scope of criminal negligence.