In high speed inkjet printing system equipped with a drying system, IR type drying system is preferable considering recent needs for compact and light-weight design. However, the IR type drying system has a risk that a cockle height changes depending on colors of ink. Thus, the authors investigated the relationship between the cockle height and exposure energy of IR heater for different colors of ink (black and magenta) by setting up an off-line drying bench. As a result, the cockle height on the area printed with pigmented magenta ink became higher than that with pigmented black ink since the absorption ratio depends on colors. Furthermore, the number of peaks in cockle profile shifts from one peak to two peaks with increasing the exposure energy. Hence, we tried to clarify the mechanism about changing of cockle profile by simulation. Physical properties such as water swelling ratio and Young's modulus of ink soaked paper were measured using a newly developed instrument. Consequently, the changing of cockle profile was reproduced by considering shrink of the non-printed area.