Spectrally encoded imaging (SEI) is a new type of tissue imaging technique in which a grating is used to encode the transverse position. In SEI, a diffraction grating and a miniature lens are used to generate a spectrally encoded line on the sample, and a line image can then be obtained without additional mechanical scanning. In combination with Fourier domain optical coherence tomography and slowly line scanning, SEI is able to provide three dimensional image and is a prospective method in endoscopic imaging. Based on analysis of the basic principle of SEI, the typical performance parameters are derived and the factors that affect lateral resolution are tested by imaging of a resolution target. It is demonstrated that the lateral resolution of SEI for the spectrally encoded line is inversely proportional to the incident light diameter and proportional to focal length of the objective lens. It is also found that the resolution in the direction perpendicular to the spectrally encoded line is poorer than that along the sit. Finally, images of onion cells are presented to demonstrate the feasibility of this technique.