Objective：To improve the diagnosis and treatment of spontaneously ruptured extensor pollicis longus（EPL） after non-oper－ative treatment of distal radius fractures. Methods：Causal analysis and standard operative treatment were conducted on 30 cases of spontaneously ruptured EPL with old distal radius fractures but without new wrist trauma. Results：Friction theory and Pressure theory would lead to EPL spontaneous rupture after distal radius fractures with or without displaced fracture. Once ruptured tendons were found，at early stage，the end to end in-situ remediation could be performed；at late stage，the reconstruction of EPL function by trans－ferring extensor indicis proprius（EIP） was more appropriate. Conclusion：Friction theory and Pressure theory need to be fully under－stood，and only the high risk factors for EPL spontaneous rupture were early found and properly treated，the lower incidence of EPL spontaneous rupture would become a reality.