A long-term stable sub-8 fs Ti:sapphire oscillator based on domestic chirped mirrors is reported. It outputs 300 mW mode-locked pulses at 86 MHz under 4 W pump power. The second order and third order of dispersion introduced by the components of the oscillator are analyzed. Two pairs of domestically designed and fabricated chirped mirrors are utilized to compensate the dispersion introduced by the crystal and the air in cavity. By precisely controlling the dispersion of chirp mirrors, the output pulses have an ultra-broad bandwidth exceeding 150 nm (FWHM) without the insertion of wedges. With the assistance of extra-cavity dispersion compensation, a pulse duration of 7.9 fs is achieved. This is the shortest pulse duration ever reported by using domestic chirped mirrors, and the shortest pulse duration achieved without intra-cavity wedges, to the best of our knowledge. Structure design and electronic feed-back loops are employed to improve the stability of the oscillator passively and actively, respectively. With the assistance of piezoelectric ceramic, the power stability within 24 h is measured to be 0.6%, which is significantly better than that without them.