Carrier-envelope phase (CEP) stabilized 6 fs ultrashort intense pulses were generated by focusing 40 fs (full width at half maximam (FWHM)) 1.1 mJ (pulse energy) intense laser pulses into the hollow fiber filled with argon gas. The input pulse was broadened by self-phase modulation and the spectrum was compressed by chirped mirrors and two titled quartz thin wedges. We applied the compressed pulse to the experiment of high-order harmonic generation and found it supporting a transform-limited 500 attosecond single pulse in time domain.