Objective To investigate the prevalence of frailty in inpatients with lung cancer and analyze its influencing factors. Methods From December 2021 to April 2022, inpatients with lung cancer in Peking Union Medical College Hospital who met the inclusion and exclusion criteria were consecutively enrolled. Their data concerning demography, medical history, nutrition and laboratory tests were collected. Fried frailty phenotype was used to assess frailty status, Nutritional Risk Screening 2002 to screen nutritional risks, and multi-frequency bioelectric impedance analysis to determine body composition. Stata/SE 16.0 was used for data analysis. Depending on data type, comparison between groups was performed using χ²test or analysis of variance.Results A total of 109 lung cancer inpatients were included, among whom 39 cases (35.8%) were of frailty, 45 cases (41.3%) of pre-frailty, and 25 cases (22.9%) of non-frailty. The prevalence of frailty was significantly higher in patients with small cell lung cancer, comorbidities and nutritional risks (χ²=6.38,14.25,12.02; all P<0.05). Multivariate logistic regression analysis showed that the number of comorbidities, muscle mass, Eastern Cooperative Oncology Group performance status, and serum albumin were independent influencing factors of frailty and pre-frailty(β=0.653, -0.980,1.169, -0.128；all P＜0.05). Conclusion Frailty or pre-frailty is common in inpatients with lung cancer. The comorbidities, nutritional status, muscle mass and physical function are strongly associated with frailty status.