The encoding gene of phytase (phyA) from Aspergillus niger XP was expressed in Pichia pastoris. For industrial applications as feed additives, the recombinant phytase must be optimally stable and active in the digestive tract with the presence of proteolytic enzymes. In this investigation, enzyme was studied on its pH, temperature properties and in-vitro digestions. The pH profiles of the enzyme showed that the recombinant phytase had two optimum pH at 2.5 to 5.0. Temperature optimum was 60°C, respectively. In-vitro characteristics showed that the recombinant phytase was not susceptible to pepsin (in stomach phase). Therefore, incubation of enzyme preparations with pancreatin revealed that proteases from pancreatin completely hydrolyzed phytase. In regard to two phases in vitro digestion, In stomach phase, phytase could digest both purified Na-phytate salt and phytate in various feedstuff. The free Pi was released in rice bran, ground soybean, Na-phytate and ground com were 5.2 umol/ml, 4.0 umol/ml, 3.2 umol/ml, and 2.12 umol/ml respectively. In the small intestine digesting phase, the concentration of Pi also slightly increased, however with a smaller amount than that of the stomach digesting phase, as the results recorded were 0.7 umol/ml for rice bran, 0.6 umol/ml for ground soybean, 0.1 umol/ml for Na-phytate salt, and 0.4 umol/ml for ground com. All obtained data show that, this enzyme could be active when introduced to feed digestion in stomach of animals.