Abstract： The discrete element method (DEM) was applied to study the bubble behavior of type D particles to analyze the formation and the growing up process of the bubble in fluidized bed, and the effect of cohesive forces on bubbles. The results of DEM simulation reveal that the formation of bubbles in fluidized bed is related to fluidizing velocity; the introduction of cohesive force causes the first occurrence of bubbling to shift to a higher fluidizing velocity. Compared with noncohesive particles, cohesive particle fluidization exhibits a smaller bubble size and lower rise velocity. In addition, the pressure and the particle velocity around the bubble are found to be sensitive to the inter-particle force.