The mean-field theory of formation of triblock copolymer superstructure is developed in the strong segregation limit, taking into account the difference in local characteristics of the blocks (widths, persistence lengths). Special attention was paid to the role of the interfacial tension coefficients at the two interfaces during formation of the triblock copolymer superstructure. It is shown that there are different mechanisms of morphology variation, guided both by the difference in local parameters of the blocks and the difference in the interfacial tension coefficient. It is also shown that a great difference in the interfacial tension coefficients at the two interfaces can lead to the formation of(1) an asymmetrical cylindrical superstructure in the case of symmetry in the local characteristics and volume fractions of the triblock copolymers and (2) a symmetrical lamellar superstructure in the case of triblock copolymers with asymmetry in the local characteristics of the blocks.