Objective To observe the level of vitamin D in patients with steroid resistant (SR) asthma, and investigate the effect of 1,25-(OH)2D3 on JNK/AP-1 and glucocorticoid receptor of T lymphocytes in SR asthmatics. Methods Sixty-two outpatients and inpatients with asthma with acute exacerbation between 2014 and 2015 were recruited in the study, including 26 cases of steroid sensitive (SS) asthmatics and 36 cases of SR asthmatics. Meanwhile 25 healthy volunteers were recruited as control. Clinical data were collected and peripheral venous blood was sampled for measuring the level of 25-(OH)D and separating the T lymphocytes. T lymphocytes were assigned to six groups, ie. a healthy control group (Group A), a SS asthmatics control group (Group B), a SR asthmatics control group (Group C), a SR asthmatics with JNK inhibitor (SP600125)+1,25-(OH)2D3 group (Group D), a SR asthmatics with JNK inhibitor (SP600125) group (Group E), and a SR asthmatics with 1,25-(OH)2D3 group (Group F). T lymphocytes were cultured for 48 hours. By the end of culture, the expression of phospho-JNK (p-JNK) and phospho-glucocorticoid receptor (p-GR) of T lymphocytes were detected by Western blot method, and the expression of c-Jun mRNA was detected by RT-PCR method. Results The level of 25-(OH) D was lower in Group B and Group C than Group A (P<0.05), and lower in Group C than Group B (P<0.05). The level of p-JNK was higher in Group B and Group C than Group A (P<0.05), higher in Group C than Group B (P<0.05), lower in Group E and Group F than Group C (P<0.05), lower in Group D than Group F (P<0.05). The level of p-GR was lower in Group C than Group A and Group B (P<0.05), higher in Group E and Group F than Group C (P<0.05), higher in Group D than Group F (P<0.05). The level of c-Jun mRNA was higher in Group B and Group C than Group A (P<0.05), higher in Group C than Group B (P<0.05), lower in Group E and Group F than Group C (P<0.05), and lower in Group D than Group F (P<0.05). The 25-(OH) D level was negatively correlated with the expression of p-JNK and c-Jun mRNA in Group C (r=–0.69, r=–0.65, P<0.05). However, there was a positive correlation between the 25-(OH) D level and p-GR (r=0.72, P<0.05). Conclusions There is a high prevalence of vitamin D deficiency or lack in SR asthmatics. 1,25-(OH)2D3 can promote the expression of p-GR by inhibiting the JNK/AP-1 signaling pathway of T lymphocytes in SR asthmatics, which may be one of the mechanisms of vitamin D to improve glucocorticoid resistance in SR asthmatics.