The self-assembly of linear ABC triblock copolymers under cylindrical confinements is investigated in twodimensional space using the real-space self-consistent field theory. The effects of confinement degrees and preferential strengths on the triblock copolymer phase behaviors with special polymer parameters are first considered. On one hand

different confinement degrees cause different phase behaviors in nanopores with the neutral surfaces. Moreover

the strongly preferential surface fields can surpass the confinement degrees and volume fractions in determing the confined phase behaviors. On the other hand

in contrast

confined morphologies are more sensitive to the variations in the A-preferential surface field strength. Subsequently

the incompatibility degrees between different blocks are systematically varied under cylindrical nanopore confinements. Under cylindrical nanopore confinements

the morphologies are very sensitive to the variations in the incompatibility degrees. Meanwhile

nanopore confinements can affect order-disorder and order-order transition points in the bulk. The corresponding free

internal

and entropic energies as well as the order parameters are also quantificationally examined to deeply investigate the confined phase mechanisms

and a number of morphological transitions are confirmed to be of first-order. These findings may guide the design of novel nanostructures based on triblock copolymers by introducing confinements.