The present invention relates to A system for monitoring the cardiovascular system using a heart sound, which comprises a heart sound receiving means(100) for receiving a heart sound(HS); DSP (Digital Signal Processor) module(200) for converting the heart sound(HS) received from said heart-sound receiving means(100) to a digital signal; and an arithmetic section(300) for calculating phonocardiogram(PCG) from the digital signal converted in the DSP module (200) and calculating information related to a preload or information related to a cardiac contractile force or information related to a respiratory change.