A new concept of the anti-freeze PEFC stack has been demonstrated. Anti-freeze concepts consist of an antifreeze coolant system and the new humidification method called “Jiko-kashitu”, which eliminates the liquid water channels required for humidificaion. The antifreeze stack has the cell stack assembly equipped with an anti-freeze coolant system and the humidifying section recycling of product water. The fresh air humidified by the Jiko-kashitu method is supplied to the cell stack assembly. The exhaust air including product water is introduced into the Jiko-kashitu section and product water permeates the membrane to humidify the fresh air. The anti-freeze stack also employs the low height design fitting under a passenger space by use of high aspect ratio separators. A 3kW class anti-freeze PEFC stack was fabricated, and the anti-freeze concepts were evaluated. Results showed that the anti-freeze stack could operate with only a little water included in a fuel gas and demonstrated a successful start up from -40 °C ambient temperature within 100 seconds after the preheated coolant is circulated.