The characteristics of the spatial beam profile of 40 GW amplified femtosecond laser pulses were studied with a homemade laser beam profile measurement system. The system was calibrated accurately and the characteristics of the spatial beam profile of femtosecond laser pulses were studied. The results indicated that the laser beam profile has better quality at lower pump current and the quality decreases as the pump current increased. The light intensity at the central area of the femtosecond laser beam may actually become weaker at high current than that at the low current. The beam quality of the pump laser had a great impact on the spatial beam profile of the femtosecond laser pulses within the multipass amplification process.