Incoherent broadband optical sources have been used in various app lications, such as fiber-optic gyro-scopes, dense wavelength division multip lexing (DWDM) , and broadband amp lification. In order to analyze the char-acteristics of a novel Er-Tm co-doped silica fiber as superfluorescent sources, the amp lified spontaneous emission (ASE) behavior is studied theoretically based on the rate and propagation equations. When the fiber is single-end pumped, the changes of pump power and total signal power along the fiber are analyzed, and the characteristics of signal spectrum as functions of fiber length, ion concentrations and pump power are discussed. When the fiber is dual- port pumped, the pump and signal power as functions of the fiber length are also discussed, and the stability of signal spectrum in different fiber length and pump power is presented. These results show that the Er2Tm co-doped silica fiber could provide more than 100nm effective ASE bandwidth,which is twice larger than the conventional singly erbi- um-doped fiberASE source, but the output power is three levelmagnitude lower than the latterASE source.