In the process of rubber extrusion, the produce of viscous heat, thermal transport and power consumption are all related to the mixing behavior of material in extruder. In this paper, numerical analyses have been carried out to study the flow and mixing behavior of the fluid in the new type of pin barrel extruder. Results show that the shorter the row pitch of pins is, the larger average mixing strength has, for example, the row pitch of pins is 48mm, 60mm, 72mm, 84mm and 96mm , the average mixing strength is respectively increased by 70%, 52%, 40%, 36% and 22% than that of conventional extruder. Meanwhile, it's also found that a decrease in row pitch of pins increases mean square deviation of mixing strength at any point but reduces extrusion flow rate. Moreover, the more the number of pins in each row is, the larger average mixing strength has. When the number of pins in each row is 4, 6 and 8, average mixing strength is respectively increased by 35%, 41% and 54%. The conclusions obtained here can provide a better reference to optimize pin layout for pin barrel extruder.