Abstract: Based on theoretic analysis on experimental data, the changes of the optical absorption and Nd3+ non-radiative transition probability caused by Fe concentration in N31 glass are discussed in detail. The optical loss at 1 053 nm and Nd3+ non-radiative energy losses increase quadratically with Fe concentration below 10-4. It is found that the optical absorption loss at 1 053 nm increases rapidly with increasing Fe concentration. However, Nd3+ non-radiative energy losses are less than 50 Hz. It is an important way to improve the laser performance by decreasing Fe concentration in melting process.