In this study, the pyrolysis of Kraft lignin was conducted in a rotary kiln reactor using rotating alumina balls as a filler to achieve a continuous pyrolysis process by the suppression of char agglomeration. Temperature variation experiments showed that the gas yield increased and the char yield decreased with an increase in the pyrolysis temperature from 550 °C to 650 °C. The maximum oil yield was obtained at a reaction temperature of 600 °C. Compared to a fixed bed reactor, a rotary kiln reactor using alumina balls produced the higher quality oil containing larger amount of organic phase oil and higher selectivity to aromatic hydrocarbons. At all temperatures, no lignin char agglomeration occurred inside the reactor due to the effective collision of lignin char intermediates and alumina balls, allowing a continuous pyrolysis process without reactor plugging.