The energy transfer mechanism between Ho3+ and Er3+ ions has been investigated in germanosilicate glass excited by 980 nm laser diode. A rate equation model was developed to demonstrate the energy transfer from Er3+ to Ho3+ ions, quantitatively. Energy transfer efficiency from the Er3+:I-4(13/2) to the Ho3+:I-5(7) level can reach as high as 75%. Such a high efficiency was attributed to the excellent matching of the host phonon energy with the energy gap between Er3+:I-4(13/2) and Ho3+:I-5(7) levels. In addition, the energy transfer microparameter (C-DA) from Er3+:I-4(13/2) to Ho3+:I-5(7) level was estimated to (4.16 +/- 0.03) X 10(-40) cm(6).s(-1) via the host-assisted spectral overlap function, coinciding with the C-DA (2,88 +/- 0.04) x 10(-40) cm(6).s(-1) from decay analysis of the Er3+:I-4(13/2) level which also indicated hopping migration-assisted energy transfer. Furthermore, the concentration quenching of Ho3+:I-5(7) -> I-5(8) transition was the dipole-dipole interaction in the diffusion-limited regime, and the quenching concentration of Ho3+ reached 4.13 X 10(20) cm(-3).