Black liquor pyrolysis/gasification is a promising alternative for conventional combustion method. The swelling of kraft black liquor was tested at 400～800℃ under nitrogen atmosphere with a visualized single droplet reactor. The main permanent pyrolysis gas components of three kraft black liquors were investigated at temperatures up to 850℃. The measurements of hydrogen sulfide release during pyrolysis were realized by iodometry, the total sulfur release was evaluated through char analysis. At the runs which temperatures higher than 500℃, the droplet volumes began decrease after the droplets swelled to the maximums. Water contents of the black liquors had no significant effects on the hydrogen yields under the reaction atmosphere where nitrogen was used as carrier gas, so nearly all the hydrogen was generated from organic components at the considered experimental conditions. The hydrogen sulfide release has similar trend to total sulfur release, i.e., the release contents reached to the maximums at about 650℃, and below or above this temperature range they decreased. 