The passively mode-locked all fiber Yb3+-doped linear laser based on the chirped fiber Bragg grating (C-FBG) combined with a semiconductor saturable absorber mirror (SESAM) is achieved. High doping concentration Yb3+-doped fiber is used as the gain medium, which is pumped by a 976 nm diode laser, with a SESAM as one end of the reflector. A C-FBG introduces a large anomalous dispersion, and operates as the other end of the reflector. Finally, a stable picosecond pulse sequence output is achieved with pulse duration of 3 ps at repetition rate of 17.07 MHz. The maximum average power is 12 mW with the center wavelength of 1045 nm. The evolution of higher-order mode-locked optical pulse is dicussed. The mode-locked fiber laser can be self-starting and has a long-time stability, and is expected to become seed sources for high-power ultrashort pulse laser.