We　investigate　the　quantum　watermark　strategy　for　quantum　images　based　on　quantum　Fourier　transform　proposed　by　Zhang　et　al.(Quantum　Inf　Process　12(2):793-803,　2013).　It　is　aimed　to　embed　the　watermark　image　into　the　Fourier　coefficients　of　the　quantum　carrier　image　without　affecting　the　carrier　image＇s　visual　effect.　However,　in　our　opinion　the　protocol　is　not　clearly　described　and　several　steps　are　ambiguous.　Moreover,　we　argue　that　the　watermarking　algorithm　claimed　by　the　authors　is　incorrect.　At　last,　a　possible　improvement　strategy　is　presented.