During plastic process, the material flow is strongly influenced by the contact area between deformed workpiece and die. In rolling process, difference of roll diameter makes the contact area between roll and deformed tape different, which leads to different material flow and the distribution of powder density. A numerical modelling of the first rolling process for 61-filament high temperature superconducting tape is constructed and the influences of roll diameters on deformation behavior of the tape are discussed. It can be found that the BiSrCaCuO (BSCCO) powder in the center of the tape has higher relative density than those in the periphery of the tape during rolling process. With the increase of roll diameter, the length of the contact arc in the roll gap expands which lead to the increasing of transversal strain and the decreasing of the related longitudinal strain. It makes the value of longitudinal strain ratio decrease gradually, which decreases the possibility of occurrence of the transversal shear band, simultaneously it increases the risk of occurrence of longitudinal crack.