The study developed and psychometrically validated the SNPMC instrument to measure the competence of surgical nurses in pain management, which consists of 78 items in seven dimensions: routine pain assessment, assessment and management of movement-induced pain and unexpected pain, pharmacological and professional pain management, pain control and patient control. The tool was created in two phases: generating items from the literature and interviews, refining through expert discussions, two Delphi rounds and analytical hierarchy; the validation included 1885 nurses from 48 hospitals in 15 regions of China. The SNPMC demonstrated high internal consistency (corrected correlations 0.672–0.847), seven-dimensional structure (loadings ≥0.40), content validity (item index 0.80–1.00; scales 0.98), and test–retest stability at 14 days. Chinese surgical nurses have achieved a medium to high level of competence. Factors associated with competence were economic region, age, professional title, department, years of experience, level of education, previous training, and continuing education in pain management. SNPMC effectively assesses competencies and identifies contributing factors.