Abstract: Objective  To investigate the relationship between serum vitamin D level and bronchial asthma in adults. Methods  We searched the CoChrane Library，  PubMed，EMbase，Web of science，OVID，Springerlink，Wiley online library，ScienceDirect，EBSCOhost，CNKI， VIP，Wanfang data databases from inception to May 1st 2017 to collect studies about the association between vitamin D and adult asthma. Two reviewers independently screened literature according to inclusion and exclusion standard， extracted data and assessed the quality of included studies.Then，metaanalysis was performed using RevMan5.3 software. Results  Nine casecontrol studies involving 827 asthma patients and 287 controls were finally included.The metaanalysis showed that 25(OH)D in adult asthma group was lower than that in control group(MD=-15.90，95%CI=-18.55-13.25，P<0.01). Adult asthma presented more vitamin D deficiency than the controls(RR=2.03，95%CI=1.572.63， I2=0%，P=0.79). In asthma patients， FEV1 % in vitamin D deficiencies was lower than that of  the normal(MD=-9.78，95%CI=-12.21-7.36，P<0.01).Conclusion  Vitamin D level is associated with asthma in adults. Vitamin D deficiency is common in patients with asthma and associated with lung function.The lack of vitamin D may be one of the potential risk factors for asthma.

Key words: asthma, vitamin D, 25(OH)D, metaanalysis, adult