Supercontinuum laser is a new direction after the emergence of super-fast laser source and also a concentrated expression of multiple nonlinear optical effects. It can be used in the fields of spectral detection, microscopic measurement, chemical sensing and so on. The supercontinuum output of both ends of the fiber is obtained by using the tunable femtosecond laser at different wavelengths output to pump the sapphire fiber. Based on the characteristics of the continuous spectrum, the supercontinuum laser system is set up taking the ensemble of an optical fiber front end and semiconductor saturable absorber mirror (SESAM) reflector as the strong resonant cavity. The center wavelength of the final output is 640 nm with the full width at half maximum more than 250 nm. The results show that the SESAM cavity can weaken noise and output consistent wide-spectrum laser.