Filamentation with and without capillary restriction by focusing intense femtosecond pulses into the Argon-filled tube was experimentally studied in this paper. The results showed that the width of the broadened spectrum was affected by the input pulse energy and position of the capillary with respect to the filament. It was also indicated that the intensity of the short wavelength region of the spectrum was enhanced by the capillary restriction, which would be favorable to obtaining intense, monocycle pulses after compression.