Disclosed is a denatured spirulina of being removed the unpleasant smell of spirulina, of maintaining its nutrients undestroyed, of being changed the unpleasant deep blue color from light blue to rose pink, and of showing higher suspensible nature to cold water, characterized in that spirulina is suspended in distilled or purified water to destroy its cell membranes by osmolytic treatment, so the chromoprotein phycocyanin leaks out of the cell membranes; chromoprotein in the spirulina is partially denatured by heating the resulting mixture; condensing, condensing under reduced pressure or finally freeze-dried the resulting mixture.