In this study, a line-focused spectral domain optical coherence tomography (LF-SD-OCT) system for imaging biological samples was built, and a data processing algorithm to improve the imaging quality was proposed to solve most of the problems of axial broadening and sensitivity attenuation caused by systematic errors. In particular, a segmented dispersion compensation method is proposed to compensate the second- and third-order dispersion phases in the imaging depth. The effectiveness and reliability of this method are verified by the imaging experiments of plane mirrors and scotch tape samples. Finally, it is proved that this method can improve the full-depth axial resolution and sensitivity without affecting the image processing speed. The final system can achieve the axial resolution of 6.76 μm and an equivalent A-scan rate of 57.2 kHz, and clearly image the tape sample within 2 mm depth and the apple sample within 0.3 mm depth. In the future, it is expected to widely realize the biological imaging applications of line-focused spectral domain optical coherence tomography.