Abstract: Objective To explore factors associated with fatigue in employees working in Internet companies.Methods A cross-sectional study was conducted among 3603 employees from 35 internet companies.A self-conducted questionnaire was used to assess employees' fatigue and related factors.Results The scores of body fatigue,mental fatigue and total fatigue were (4.53±2.56),(2.37±1.64),and (6.90±3.55)respectively.The body fatigue is positively correlated with job burnout and musculoskeletal disorders (r=0.426,0.485);the mental fatigue is positively correlated with job burnout (r=0.429).JDC and ERI occupational stress,burnout and high level of musculoskeletal disorders increased the risk of body fatigue of which odds ratios are 1.58,1.72,4.08 and 5.91;odds ratios for the risk of mental fatigue are 1.73,1.37,2.61 and 2.08.Sleep time over 7 hours reduces the risk of fatigue (P<0.05) with odds ratio of 0.61 and 0.62.Conclusion Employees of Internet companies is facing fatigue issues.To protect employee's physical and mental health is highly important for employers to alleviate fatigue and improve work performance.