Fuel cell using liquefied petroleum gas (LPG) as fuel have never been operated for a long period of time in Japan. Our company started verification research of phosphoric acid fuel cell (PAFC) using LPG as the fuel at the end of May, 1992 for a scheduled period of about three years. This paper is described two PAFC technics. One is the effective maintenances of the PAFC system in addition to suitable condition for reforming. LPG-reformer is operated by conventional nickel-groupe catalyst and new noble-group catalyst; the former invited pressure loss growing by carbon deposition, the latter keep stable reforming. And, as the value of steam carbon ratio (S/C) reduces, the waste heat increases. The demonstration PAFC was operated over 3, 000 hours on condition that S/C=3.0 (with the rated S/C=3.5) for LPG. The other is estimation of performance history of fuel cells by analyzing polarization curves; ohmic, activity, and concentration polarization components.