A swept source endoscopic optical coherence tomography system was designed with the grin-lens, single mode fiber and fiber optic rotary joint for endoscopic imaging. The effects of the pitch of the grin lens and the distance between the single mode fiber and the grin-lens on system performance were then analyzed with Zemax. The object distance of 0.7 mm was chosen according to the diameter of esophagus and the Pitch of 0.24P was chosen according to the cost and the effects analyzed above. The measurement results shown that the axial resolution of the system is ~9 μm and the lateral resolution is ~19.5 μm with the imaging depth of 6 mm in air. The working distance of the probe is about 7 mm. The initial cross-sectional images of the intestinal tract of pig were presented to demonstrate the capability of the system for endoscopic applications. And all these results demonstrated that the probe designed is suitable for endoscopic imaging of esophagus.