Objective To analyze the correlation between sagittal orientation of lumbar pedicle screw and screw loosening based on craniocaudal cyclic load and artificial vertebra, and to provide a reference for improvement of pedicle screw orientation during surgery thus reducing the incidence of screw loosening postoperatively. Methods The pedicle screws were inserted into artificial vertebra via cranial orientation, parallel orientation and caudal orientation respectively. After installation in the material testing machine, the model was subjected to a 100N preload and 166N cyclic load for 10,000 cycles. During the test, displacements were recorded and cycle-displacement curves were drawn. After test and removal of screw, the screw hole volume was measured, and the screw hole volume ratio (the ratio of screw hole volume to the volume of the screw inserted into the vertebra) was calculated. Results The cyclic-displacement curves showed that the cranial group had the largest displacement; parallel group was the second, and the last was the caudal group. Screw hole volume ratio result showed that cranial group had the highest ratio, and followed by parallel and caudal groups. Correlation analysis showed that negative relation was found between sagittal orientation of pedicle screw and the terminal displacement (the displacement corresponding to the 10,000th cycle) (p=-0.897, P=0.02) as well as screw hole volume ratio (p=-0.902, P=0.01). Conclusion Sagittal orientation of lumbar pedicle screw related negatively to the screw loosening, which indicated the adjustment of orientation from cranial to parallel and even caudal one at a certain angle would reduce the incidence of screw loosening.