The conformation and self-assembly of tertiary butyl-phenyl substituted Pt-porphyrin (Pt-TBPP) on an Ag(110) surface have been studied as a function of deposition and annealing temperatures using scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). While a stable two-dimensional arrangement is formed by room-temperature deposition, one-dimensional chains of Pt-TBPP along the [110] direction are assembled by decreasing the deposition temperature, wherein the molecular orientation is orthogonal to that formed at room temperature. From a careful comparison of STM images and molecular orbital calculation results, the molecular conformations within these assembled structures were determined by the bending angles of the tertiary butyl-phenyl substituents, as well as the rotation angles, which result from conformational adaptation of the adsorbed Pt-TBPP to the substrate lattice. We also observed the structural transformation from one-dimensional chains formed at low temperature to the two-dimensional arrangement by thermal annealing at 280-310 K.