A method of forming a color picture tube fluorescent screen by so-called dry process. After a photosticky substance mainly containing a diazonium compound is coated on a panel inner face, phosphor is adhered to portions of the compound which have been exposed to light through a color selection electrode and rendered sticky, and surplus phosphor applied on unexposed portions of the compound is removed, the above steps being consecutively repeated for phosphors of three colors to form picture elements of triads of three color phosphors on the panel inner face. The panel inner face is then treated with an aqueous solution containing at least polymer coagulant.