The aim of this study (a clinical trial) is evaluating the effect of vitamin D deficiency treatment on relieving the clinical Symptoms and spirometric indices in patients suffering from COPD. Sixty patients who are suffering from COPD and vitamin D deficiency (less than 30ng/dl), are 30-80 years old enter the research based on inclusion Criteria. These patients are selected from lung clinic in Valiasr hospital. Then Patients are divided to 2 group and each group have 30 patients through simple random sampling method. In First group (drug group), one 50000 IU purl of vitamin D, every week for 3 continuous months and one calcium-D tablet daily will be prescribed in addition to standard COPD treatment. Second group (placebo group) will receive placebo, every week for 3 months in addition to standard COPD treatment. At the beginning and after 3 months, the spirometry process and measurement of 25 OH vitamin D, Calcium (ca), Phosphorus (p), Albumin and Parathyroid Hormone (PTH) will be performed for all patients. Every month Patients will be controlled from the perspective of drug consumption and correct using of it and they will be excluded if the exclusion criteria met (renal disease, liver disease, parathyroid disease, malnutrition, malabsorption). In this study, increase of Forced expiratory volume during the first second (FEV1), Forced expiratory volume during the first second / Forced Vital Capacity (FEV1/FVC) and 25 (OH) Vit D in first group compared to second group as a primary consequence and reduction of Dyspnea severity based on MRC criteria in first group compared to second group, will be discussed as secondary outcome.