This study includes an isolation and partial purification the protenases from human plasma in city center of Mosul. Three proteinous components had been isolated by gel filtration technique from the precipitate produced by saturation ammonium sulfate. It was found that the peak (A) had a high activity of protenases using sephadex G-75. The apparent molecular weight of the isolated protenases the peak (A) using gel filtration was (75000± 1000 Da). Maximum activity for protenases was obtained using (0.32) mM of casein as substrates, phosphate buffer (50 mmol) at PH (7.5) for (10) minutes in incubation at (45) °C. Using Line Weaver-burk plot were the maximum velocity (0.796) U/ml and Michaelis constant (0.035) mmol. EDTA and thiourea inhibition on the protenase activity, while magnesium sulfate and calcium chloride shown increase activity.