Background:Airflow resistance in asthma caused by changes in the airways that is bronchoconstriction, airway edema, airway hyperresponsiveness and airway remodeling. Vitamin D supplementation is expected to raise the value of the measurement of FEV1/ FVC in patients with asthma controlled in part through the role of vitamin D in terms of antiviral effects, atopic response, response improvement steroid and prevent airway remodeling process.Objective:Comparing the measurement values of FEV1/ FVC in patients with asthma controlled most of which do not get supplemental vitamin D than getting supplemental vitamin D.Methods:This study is a randomized experimental simple study. This research was conducted in dr Soetomo Hospital from June to July 2015. The sampling technique using consecutive sampling. Samples were divided into two groups each consisting of 14 samples which have earned a combined therapy of inhaled corticosteroids and LABA. The control group that was not given additional vitamin D supplementation and the treatment group were given supplements of vitamin D for 1 month. Measurement and main result:Testing of data distribution using the ShapiroWilk method because the sample size is less than 50. The result of the difference in FEV1 / FVC with a paired sample t - test is known that in the control group (not given additional vitamin D supplements) did not occur significant difference (p = 0.219> 0.05), while the treatment group (given additional vitamin supplements D) proved significant difference (p = 0.020 <0.05) where the value of FEV1 / FVC after being given additional vitamin D supplements increased to 96.071% of the initial conditions is 84.786%.Conclusions:The measurement values of FEV1/ FVC in patients with asthma controlled most of which get vitamin D supplementation are the most significant increase compared to the control group who did not receive supplementation ofvitamin D.