We present the studies of Raman scattering spectra from blue light-emitted ladder type organic conjugated polymers, methyl substituted ladder type poly(p-phenylene), m-LPPP, under hydrostatic pressure of 0–50 Kbar in order to investigate the structure and to observe the phase change. We find that the Raman spectra shift to higher frequency under hydrostatic pressure. We also find that the shift rate and the change of intensity of the Raman peaks from backbone and side chain vibrations are different. By this work and the studies of the optical properties of the m-LPPP polymers under hydrostatic pressure, we could understand the effect of the molecular structure to its optical properties.