Impedance pulmonary arterial pressure(PAP) measuring instrument with a microcomputer was designed and manufactured. It performs the functions of graphic analysis, logic judgment and mean pulmonary arterial pressure (PAP) measurement. Impedance information obtained by impedance PAP measuring instrument with a microcomputer was consistent with that by type HB-3COG apparatus. This new instrument has many advantages, such as reliability, saving of time and efforts as well as simplicity in operation.