Pressure induced phase transitions were found in spin ladder compounds SrCu2O3 and Sr2Cu3O5 by powder X-ray diffraction (XRD) experiment with diamond anvil cell (DAC) and synchrotron radiation. The structure of the HP phase of SrCu2O3 was successfully solved by Rietvelt analysis. In the orthorhombic structure (space group Pmmn) with unit-cell parameters of a=10.628Å, b=3.885Å and c=3.282Å, the Cu2O3 planes at SrCu2O3 became "fluttering" as that of CaCu2O3. Application of an external pressure induced a structural transition as a substitution of smaller cation (Ca for Sr) did.
