We present a passive flow-rate regulator, capable to compensate inlet pressure variation and to maintain a constant flow-rate for precise liquid control. Deflection of the parallel membrane valves in the passive flowrate regulator adjusts fluidic resistance according to inlet fluid pressure without any external energy. Compared to previous passive flow-rate regulators, the present device achieves precision flow regulation functions at the lower threshold compensation pressure of 20kPa with the simpler structure. In the experimental study, the fabricated device achieves the constant flow-rate of $6.09{pm}0.32{mu}l/s$ over the inlet pressure range of $20{sim}50$ kPa. The present flow-rate regulator having simple structure and lower compensation pressure level demonstrates potentials for use in integrated micropump systems.