The influence of erbium doped concentration on the pump efficiency and wavelength stability of erbium doped fiber source was researched. Five type fibers were applied in single pass backward source respectively. And the outputs of the five sources were compared. The pump efficiency of erbium doped fiber source is increased as the erbium concentration increases. Cluster effect becomes obvious at high concentration and the pump efficiency is reduced by 20%. The pump threshold value is increased from 18.3 mW to 32.4 mW as the concentration increases. The excellent erbium doped fiber length is decided by the erbium concentration in proportion from experiment results. And the relationship between pump wavelength and source mean wavelength is not influenced by erbium concentration. The temperature stability of source with lower erbium concentration is almost 100 ppm better than that with higher erbium concentration. The optimum erbium concentration is about 110 mol according to experiment.