Samarium doped aluminosilicate fiber was fabricated by modified chemical vapor deposition (MCVD) process.The optical properties of this fiber were characterized by white light source and OSA.The photodarkening property of the fiber was measured by an Ar+ laser. The experiment results proved that the samarium doped aluminosilicate fiber had better photodarkening resistance than that of the samarium doped germanosilicate fiber. A brief explanation showed that the photodarkening loss could be reduced by changing the fiber core’s material from germanosilicate to aluminosilicate. Samarium doped aluminosilicate fiber was very promising for the red fiber laser application. Samarium doped aluminosilicate fiber was fabricated by modified chemical vapor deposition (MCVD) process.The optical properties of this fiber were characterized by white light source and OSA. The photodarkening property of the fiber was measured by an Ar + laser. The experiment results proved that the samarium doped aluminosilicate fiber had better photodarkening resistance than that of the samarium doped germanosilicate fiber. A brief explanation showed that the photodarkening loss could be reduced by changing the fiber core’s material from germanosilicate to aluminosilicate. Samarium doped aluminosilicate fiber was very promising for the red fiber laser application.