Spectral beam combining is an effective way to break through the power limitation of a monolithic fiber laser and achieve high brightness fiber laser output. A spectral beam combining scheme was presented that the single element was structured by external-cavity fiber oscillator. This scheme had more compact structure and was able to contain more elements, compared with the current MOPA structure element. A theoretical analysis was conducted about the relationship between the wavelength and position of each element, and a numerical simulation was carried out about the influence of aberrations in the transform lens on cavity loss and combining effects. An experimental system was built, and the experimental results agree well with the theoretical analysis. This work has important guiding significance for the building of next generation spectral beam combining system.