The absorption and upconversion spectra of Er3+-doped heavy metal oxyfluoride germanate glass were investigated, and upconversion mechanisms of Er3+ in the glass were analyzed. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime τrad of each energy levels for Er3+ were calculated by Judd-Ofelt theory. The results showed that the intense green and weak red emissions were observed, a two-photon upconversion process was assigned to the green and red emissions, and the possible upconversion mechanisms were involved in excited state absorption and energy transfer between excited Er3+ ions. Raman spectrum indicated the fluoride ions in the glass network had important influence on upconvesion fluorescence.