The spectrum features of the Amplified Spontaneous Emission（ASE）of a 25cm-long Er-doped fiber pumped by980 nm LD is measured

and its ASE empirical formula is obtained from the experimental data fitting by using the L-M algorithm and the least square method.The research results indicate that the central wavelength of the two peaks in the ASE spectrum are 1 530.951 and 1 555.964 nm respectively and the goodness of fit（R-square）value reaches 0.980 72 and the residual sum of squares is 4.447 69×10-9.