We study the homogeneity of Pythagorean orthogonality in normed linear spaces． It is proved thatPythagorean orthogonality is unique at x if x is a homogeneous direction of Pythagorean orthogonality． At the sametime，we study the ralation between homogeneous direction of Pythagorean orthogonality and other notions includingisometric reflection vectors and L2 - summand vectors，and show that a Banach space X is a Hilbert space if and onlyif the relative interior of the set of homogeneous dierections of Pythagorean orthogonality in the unit sphere of X isnot empty． We introduce a geometric constant NPX to measure the non- homogeneity of Pythagorean orthogonality． Itis proved that NPX = 0 if and only if X is a Hilbert space．