Neutral protease which was obtained from a genus of Aspergilli as the crystal form were investigated for their purification and properties. The results of biochemical and enzymatic studies for their purification and properties in this enzyme were as follows. 1) On the wheat media containing 70%-water and $CaCo_{3}$, Aspergilus oryzae S.H.W. 131 is satisfactorily grown under the basic optimum conditions temperature $27^{circ}C$- $30^{circ}C$at relative humidity 100% for three days. 2) The enzyme solution extracted with water is successively purified through the passing on column of Asmti-177N for decolorization of it. And ion exchanger such as DEAAE Sphadex A-50 or Shepadex G-100 and fraction collector is necessary for the sepearte treatments of this enzyme. After washing it with organic solvents as aceton-EtOH, etc., it should be dried on the vacuum dryer at $40^{circ}C$) The protease activity is determined by the amounts of amino acids, tyrosine. 4) The optimum pH of neutral protease is 6.0-8.0. 5) In effectively decomposing with this neutral protease, the optimum temperature is $35^{circ}C$. 6) It is interesting that the amounts of metal ion affects the activity of neutral protease. For examples, if it were treated with manganic ion, its activity would be more effective than any other that.