Background Recognizing the kinematic characteristics of lumbar facet joints is important for the prevention and treatment of lumbar degenerative diseases. Previous studies have been conducted in either the supine or standing position, and there are no measurements regarding the kinematic characteristics of the lumbar facet joints while sitting. The aim of this study was to measure and analyze lumbar facet joint motion characteristics while sitting. Methods Ten subjects (5 males and 5 females) performed the movements of flexion-extension, left bending-right bending, and left rotation-right rotation in a sitting position. Dual Fluoroscopic Image System and computed tomography technique were used to measure the displacement and rotation angle of the lumbar facet joints of the subjects for analysis. The movement characteristics of L3-S1 were measured. Results When the subjects were in sitting position, the lumbar vertebra mainly changed in Z-axis and alpha, beta angle when they performed flexion-extension activities. The displacement of the left facet joint was 4.65 +/- 1.99 mm at L3-4, 1.89 +/- 2.99 mm at L4-5, and 0.80 +/- 2.27 mm at L5-S1 in the Z-axis, and the displacement of the right facet joint was 3.20 +/- 2.61 mm at L3-4, 1.71 +/- 3.00 mm at L4-5, and 0.31 +/- 1.69 mm at L5-S1 in the Z-axis. The rotation in the alpha angle was 6.00 +/- 4.49 degrees at L3-4, 3.51 +/- 5.24 degrees at L4-5, and 0.97 +/- 4.13 degrees at L5-S1, which was significant different. The rotation in the beta angle was 2.30 +/- 2.94 degrees at L3-4, 0.16 +/- 2.06 degrees at L4-5, and 0.35 +/- 1.74 degrees at L5-S1, which was significant different. When the lumbar spine performed the activity of left bending-right bending, there were changes in rotation mainly in the Z-axis and beta angle. The displacement of left facet joint in the Z-axis was 1.34 +/- 2.84 mm at L3-4, 2.11 +/- 0.88 mm at L4-5, and 0.72 +/- 0.81 mm at L5-S1; the rotation in the beta angle was 5.66 +/- 2.70 degrees at L3-4, 7.89 +/- 2.59 degrees at L4-5, and 1.28 +/- 2.07 degrees at L5-S1; when the lumbar spine performed the activity of left rotation-right rotation, there were changes in the beta angle. The rotation of beta angle was 4.09 +/- 2.86 degrees at L3-4, 2.14 +/- 3.38 degrees at L4-5, and 0.63 +/- 1.85 degrees at L5-S1. Conclusion The lumbar facet joint motion in sitting position is different in each mode of motion. The horizontal displacement and rotation are predominant during flexion and extension activities, while there are different rotation in bending and rotation. The study shows the coupled motion of the lumbar facet joints while sitting, providing a new perspective on the kinematics of the lumbar spine and the etiology of lumbar degenerative diseases.