The nonlinear two-photon absorption of Nd ions in Nd-doped laser glasses was studied with single picosecond laser pulses from a mode-locked Nd glass laser.With the aid of ex- periments and theoretioal oaleulations,we obtained the cross section for two-photon absor- ption of Nd ions σ=(6.16±1.1）×10-33cm4/W,the nonlinear absorption coefficient r= (1.65±0.29）×10-12cm/W and profiles for the function relationship between the optical intensity and the transmissivity.The peak output intensity for Nd glass amplifiers is limi- ted by two-photon absorption.It was determined experimentally that the maximum peak intensity of the amplifiers is Imax=(4.15±0.73）×1010W/cm2.