偏倚在外科研究中是常见的影响研究质量的重要原因，产生的原因与外科医师的理念和外科临床的特点所致的设计存在缺陷有关。因此，研究中纳入合理的研究对象、采用更科学的设计方案、设立严格的对照、使用盲法观测和客观的检测指标是避免偏倚的重要措施。结论：偏倚是影响外科研究质量的重要因素，避免或减少偏倚的惟一办法是实施科学严格的科研设计。

Causes to leading to bias and common bias in clinical researches of surgery LIU Xu-bao.Department of General Surgery, Huaxi Hospital, Sichuan University,Chengdu610041,China Abstract Bias is leading causes to decrease reliability of surgical research. Philosophy of Surgical doctors and clinical character of surgery may be correlated with defect in research design, which is cause of bias. So to avoid bias in research, a series of interventions should be applied, such as to select relatively strict target objectives, to use scientific proposal of design, to adopt reasonable control, and to apply blind observation and objective detections. Conclusion: bias is important factor to decrease research quality of surgery. Only way to abate or avoid bias is use scientific proposal of design in researches.