Numerical simulation on high concentration tellurite EDFA is based on four energy-level model.The main characteristic of gain and noise figure both in C-band and L-band is presented.The bandwidth achieves 85 nm when gain of amplifier both in C-band and L-band achieves above 20 dB.Furthermore,the degradation of gain and noise characteristic caused by the effect of upconversion which is brought by high concentration is analyzed.The degradation is 4% in C-band and 10% in L-band.The degradation is decreasing when the pump power increasing.It is just 0.1% when the two-stage amplifier is bi-directional pumped.