Abstract: Based on the rate equations and light propagation equations,the model of Er3+/Yb3+ co-doped double clad fiber amplifiers has been discussed,and the population distribution characteristics of Er3+ upper level in Er3+/Yb3+ co-doped double clad fiber amplifier pumped at 980nm bands have been analyzed by using the results of numerical simulation.The normalized population distribution curves of Er3+ upper level have been obtained under two different pump schemes,namely co- and counter-propagations. The distribution characteristic of signal has also been analyzed by using the normalized population distribution curves of Er3+ upper level.