To obtain the temperature-sensitive rate equations, a new energy level diagram of Praseodymium ion (Pr3+) in a glass host is modelled. By solving the modified rate equations, an analytical expression is presented to investigate the temperature dependence of the signal gain of a praseodymium-doped fiber amplifier (PDFA). It is seen that a change in the signal gain slightly depends on the variation of the distribution of Pr3+-ions in transitions F-3(4) <-> F-3(3) with the temperature. Numerical calculations are carried out for the temperature range which is changing from -20 to +60 degrees C. Pr3+-doped ZBLAN fiber amplifier pumped at 1017 nm and Pr3+-doped sulfide fiber amplifier pumped at 1028 nm are selected as an application for the 1.3 mu m signal wavelengths. It is also seen that the prediction of the model is in good agrement with their experimental results. (c) 2006 Elsevier B.V. All rights reserved.