The pulse width generated by an ultra-broad-bandwidth Ti: sapphire oscillator is measured using SPIDER technique. The measurement result is 7.86 fs, which is, as presently reported in China, the shortest pulse output directly from an oscillator in which only chirped mirrors was used to compensate for the laser dispersion. Layout of the oscillator and the SPIDER setup are introduced in details, and the spectral phase of the laser pulse obtained through calculation is discussed.