A process for the joint preparation of 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropene, comprising: (a) starting materials comprising at least one compound having the structure of formula I, II or III is reacted with hydrogen fluoride, producing 1,2,3-trichloro-3,3-difluoropropene, 1,2,3-trichloro-1,1,2-trifluoropropane, and 1,2,3-trichloro-1,1,3-trifluoropropane; in the compounds of said formulae CF2−mClm=CCl-CHF2−nCln (Formula I), CF3−pClpCHCl=CH2Cl (Formula II), and CF3−xClxCF2−yClyCHF2−zClz (Formula III), m=0, 1, 2; n=1, 2; p=2, 3; x=1, 2, 3; y=1, 2; z=1, 2 and 4≦x+y+z≦6; (b) the 1,2,3-trichloro-3,3-difluoropropene, 1,2,3-trichloro-1,1,2-trifluoropropane and 1,2,3-trichloro-1,1,3-trifluoropropane undergo dechlorination, producing 3-chloro-3,3-difluoropropyne, 3-chloro-2,3,3-trifluoropropene and 3-chloro-1,3,3-trifluoropropene; and (c) the 3-chloro-3,3-difluoropropyne, 3-chloro-2,3,3-trifluoropropene and 3-chloro-1,3,3-trifluoropropene are reacted with hydrogen fluoride, simultaneously yielding 1,3,3,3-tetrafluoropropene and 2,3,3,3-tetrafluoropropen.FIG. 1 is designated as the drawing of the Abstract.