The utility model discloses a circulation formula steam generator, including the vaporizer, the inlet tube of one end in the vaporizer top penetrates to it, the overboard steam drain pipe of one end in the vaporizer bottom penetrates to it to and the electric heat temperature control device of cover on the vaporizer lateral wall, the flow distribution plate includes the plate body to and the mobile hole of vapour -liquid in the inside both sides of plate body is seted up to the symmetry, vaporizer inside is equipped with two at least flow distribution plates that are stacked by last down layering, and the mobile hole of vapour -liquid on two adjacent flow distribution plates is 90 crisscross distributions, and the space between flow distribution plate and vaporizer top, two adjacent flow distribution plates, flow distribution plate and vaporizer bottom has all been filled up stainless steel theta ring completely and has been packed. The utility model discloses comparing traditional steam generator, can realizing the online real -time vaporization of aqueous water, the inside no aqueous water of pipeline is remained to can control the production speed of steam through the injection speed of aqueous water, the while can obtain the desired temperature's steam under the ordinary pressure very conveniently.