A method for co-producing 2,3,3,3-tetrafluoropropene and trans-1,3,3,3-tetrafluoropropene, characterized in that comprising following steps of: preheating a mixture of 1,1,1,2,2-pentachloropropane and 1,1,1,3,3-pentachloropropane together with anhydrous hydrogen fluoride and simultaneously introducing into a first reactor to react in the presence of a catalyst La 2 O 3 -Cr 2 O 3 at a reaction temperature of 200-350°C, a molar ratio of the anhydrous hydrogen fluoride to the mixture of 1,1,1,2,2-pentachloropropane and 1,1,1,3,3-pentachloropropane is 6-18:1, with a contact time of 1-20s to obtain a first reactor product; directly introducing the first reactor product obtained in the step into a second reactor without separation, and carrying out a catalytic fluorination reaction in the presence of a catalyst Ga 2 O 3 -Y 2 O 3 -Cr 2 O 3 at a reaction temperature of 250-400°C, with a contact time of 1-35s to obtain a second reactor product; introducing the second reactor product obtained in the step into a first separation column for separation to obtain a first separation column bottom component and hydrogen chloride; introducing the first separation column bottom component obtained in the step into a second separation column for separation to obtain a second separation column overhead component and a second separation column bottom component; washing the second separation column overhead component obtained in the step with water and an alkali, drying, and then introducing into a third separation column to obtain a third separation column overhead component and a third separation column bottom component; introducing the third separation column bottom component obtained in the step into a fourth separation column to obtain a 2,3,3,3-tetrafluoropropene product and a fourth separation column bottom component; and introducing the fourth separation column bottom component obtained in the step into a fifth separation column to obtain a trans-1,3,3,3-tetrafluoropropene product. preheating a mixture of 1,1,1,2,2-pentachloropropane and 1,1,1,3,3-pentachloropropane together with anhydrous hydrogen fluoride and simultaneously introducing into a first reactor to react in the presence of a catalyst La 2 O 3 -Cr 2 O 3 at a reaction temperature of 200-350°C, a molar ratio of the anhydrous hydrogen fluoride to the mixture of 1,1,1,2,2-pentachloropropane and 1,1,1,3,3-pentachloropropane is 6-18:1, with a contact time of 1-20s to obtain a first reactor product; directly introducing the first reactor product obtained in the step into a second reactor without separation, and carrying out a catalytic fluorination reaction in the presence of a catalyst Ga 2 O 3 -Y 2 O 3 -Cr 2 O 3 at a reaction temperature of 250-400°C, with a contact time of 1-35s to obtain a second reactor product; introducing the second reactor product obtained in the step into a first separation column for separation to obtain a first separation column bottom component and hydrogen chloride; introducing the first separation column bottom component obtained in the step into a second separation column for separation to obtain a second separation column overhead component and a second separation column bottom component; washing the second separation column overhead component obtained in the step with water and an alkali, drying, and then introducing into a third separation column to obtain a third separation column overhead component and a third separation column bottom component; introducing the third separation column bottom component obtained in the step into a fourth separation column to obtain a 2,3,3,3-tetrafluoropropene product and a fourth separation column bottom component; and introducing the fourth separation column bottom component obtained in the step into a fifth separation column to obtain a trans-1,3,3,3-tetrafluoropropene product.