Graphene, as a saturable absorber (SA), has attracted much attention for its application in ultrashort pulse fiber lasers due to its ultrafast interband carrier relaxation and ultra-broadband wavelength operation. Nevertheless, during the stacking process of monolayer graphene layer, the induced nonuniform contact at the interface of graphene layers deteriorate the device performance. Herein, we report the fabrication of graphene saturable absorber mirrors (SAMs) via a one-step transfer process and the realization of the much enlarged modulation depth and the much reduced nonsaturable loss with tri-layer graphene (TLG) than single-layer graphene (SLG) due to the improved uniform contact at the interface. Moreover, the operation of 1550 nm mode-locked Er-doped fiber laser with the TLG SAM exhibits excellent output characteristics of the maximum output power of 9.9 mW, a slope efficiency of 2.4% and a pulse width of 714 fs. Our findings are expected to pave the way toward high-performance ultrashort pulse fiber lasers based on graphene SAs.