A Kerr-lens mode-locked femtosecond Nd:LMA laser pumped by laser diode is discussed. Through calculation and theory analysis, a Kerr-lens mode-locked femto-second Nd:LMA laser operating at wavelength of 1054 nm is demonstrated by using additional Kerr medium (SF57) with the large nonlinear coefficient and optimal cavity design. The transform-limited pulses as short as 610 fs duration, corresponding to spectra width of 2.1 nm, were obtained in this experiment, and laser output power is 15 mW.