Background The aim of the present study was to test the body composition changes of patients undergoing elective craniotomy using bioelectrical impedance analysis, so as to evaluate the effect of enhanced recovery after surgery (ERAS) to nutritional status of patients. Methods 140 patients who needed elective craniotomy were randomly divided into two groups: observation group (ERAS group) and control group (traditional treatment group). The age was 45.6 ± 12.7 years old. Patients in ERAS group were treated with a set of enhanced recovery measures, while control group patients underwent conventional treatment. Bioelectrical impedance analysis was used to test body composition before and after the surgery. Results The body mass (BM), body mass index (BMI), fat mass (FM), muscle mass (MM), fat mass index (FMI), free-fat mass index (FFMI), body cell mass (BCM), body cell mass index (BCMI), in both groups were decreased after surgery. The decrease of FM and FMI in the control group was significantly different from that in the observation group (p<0.05). However, the decrease of BM, BMI, MM, FFMI, BCM and BCMI in both groups were not statistically significant. Conclusion Patients undergoing elective craniotomy showed various degrees of nutritional injuries, and ERAS could alleviate nutritional injuries caused by operation. Keywords Enhanced Recovery after Surgery • Bioelectrical impedance analysis • Elective craniotomy Trail Registration Chinese Clinical Trial Registry, ChiCTR-INR-16009662. Registered on 27 October 2016. Trail Registration Chinese Clinical Trial Registry, ChiCTR-INR-16009662. Registered on 27 October 2016.