An improved design principle of Model of 1-1 OPCM sensor elements is proposed from the constitution and mechanics-electric coupled property of OPCM. The orthotropic ratio is defined and the optimal ratio of length to width of Model of 1-1 OPCM sensor is deducted from it. The functional properties of an OPCM sensor designed by the optimal ratio of length to width are simulated with COMSOL. The numerical results are validated by experimental data. Experimental results agree well with the results of numerical simulation.