The simple adaptive control (SAC) method being applied to non-ASPR plants including pneumatic servo systems, it becomes indispensable to furnish a parallel feedforward compensator (PFC) to the system. Also, a fine adjustment of parameters in PFC is required to keep stability and to attain a desirable performance. It is, however, difficult to adjust them suitably with little information on the plant. In this paper, we propose an algorithm which tunes them automatically with a watch of improvement of the actual performance. An experiment is also carried out to show the effectiveness of our proposal.