The invention discloses a production method suitable for directly heating a steel sheet billet for a pressure vessel. According to the method, on an existing continuous casting machine, the front endlarge press for casting blank structure adjustment and control technology, the solidification tail end position indetermination soft press technology and the hot roll gap reproduction technology are adopted for producing the high-quality steel (Q420R) continuous casting sheet billet for the pressure vessel; after continuous casting of the sheet billet is completed, the sheet billet is directly putinto a furnace for heating and rolling; small components of the sheet billet are segregated, the in-furnace component balancing time of the sheet billet can be shortened, thus, the heating time of the sheet billet is shortened, and the direct heating requirement for the sheet billet is met; by means of expansion of an equiaxed crystal zone in the sheet billet, cohesion and segregation, at the half thickness, of inclusions and components are reduced; and a produced steel sheet is uniform in performance.