Abstract: A total of 210, 3-d-old Japanese quail chicks (Coturnix japonica) allocated to 21 cages, each cage containing 10 chicks, that were received seven diets with three replication of each diet. Experimental diets were arranged with five levels 150, 300, 600, 1200 and 2400 phytase enzyme unit (FTU kg-1) with commercial name (Natuphos 500) as treatments1, 2, 3, 4 and 5, respectively and two control groups (positive and negative controls). At the end of each experimental period (each week to 45 days of ages), birds were weighed and feed consumption was recorded for feed efficiency computation. At the age of 45 days, four chicks were randomly selected from each treatment blood samples for subsequent determination of minerals (Ca, P and Mg) and alkaline phosphates (ALP) in serum. Data were subjected to analysis of variance using the General Linear Models (GLM) procedures of SAS software. Data showed that feed efficiency was not affected at periods of 9-16 and 37- 45 days of ages by addition of phytase, but in other periods were significantly different (p<0.05). Liver weight in treatment 5 (4.68±0.23 g) at 45 days of age was more than other groups that had significant difference (p<0.05). Quails of treatment 4 had Calcium (Ca) and Phosphorus (P) 10.19±0.80, 7.11±0.46 mg dL-1, respectively that were more than other groups. The amount of Magnesium on treatment 1(3.27±0.15 g), positive control (3.27±0.15 g) and negative control (3.56±0.15 g) which were not significantly different (p>0.05), whereas treatment1 and control groups had significant differences with other treatments (p>0.05). The Alkaline phosphates of treatment 5 (366.83±38.07 IU L-1) in blood serum at 45 days of age represents the most increase among other treatments, which had significant differences with treatment 1 (124.99±50.80 IU L-1) and control groups, although weren’t significant difference with the treatments 2 (260.26±50.01 IU L-1) and treatments 3 (288.37±40.64 IU L-1).