First, the drying and devolatilization characteristics of a lignite washery tailing (LWT) particle in a fluidized bed (FB) are studied, including particle weight loss, size change, temperature change, drying, devolatilization, and agglomeration properties. The effects of the temperature of FB reactor and the initial moisture content of an LWT particle are also examined. The shrinkage ratio of an LWT particle is experimentally established as a key parameter for the drying and devolatilization model. Furthermore, by coupling the drying model, shrinkage model, and combustion of volatiles and char, a comprehensive model describing the drying and devolatilization processes of an LWT particle during its combustion in an FB is proposed. Three corrections are added in this model, i.e., a drying rate correction, particle shrinkage correction, and volatile and char combustion correction. The results show that the drying rate, devolatilization, and center temperature of an LWT particle better represent the experimental data after coupled improvements in the model. Accurately describing these two processes, i.e., drying and devolatilization, will improve the stability and operating conditions of an FB system when firing LWT particles.