Abstract: Eighty-four Hy-line pullets at 19 weeks of age as a commercial egg strain were used and divided into 12 groups (4 treatmentsx3 replicates). A corn-soybean meal basal diet formulated and served as control. The basal diet was supplemented with three levels of phytase (500, 750 and 1000 FTU kg-1 of feed) for treatment groups, two and three, respectively. To evaluate, the effect of phytase supplementation on egg number, egg weight and egg mass egg production, feed consumption, feed conversion ratio and determine minerals. The results show that the addition of phytase increased egg number, overall egg number, feed consumption and feed conversion ratio but the difference not significant. The effects of phytase supplementation on egg quality did not show any significant effect on egg quality measurements excepted egg weight mean shell thickness, shell breaking, shell percentage and Huag unit. Also, it can indicated that phytase supplementation significantly improved calcium (Ca), phosphours (P), magnesium (Mg) and potassium (K) in serum from the present study it can concluded that phytase supplementation at level (1000 FTU kg-1 of feed) in period second four months and third four months had significant effect on most of laying hen performance, egg quality and some blood parameters.