Objective To discuss the effects of titanium nickel shape memory alloy (TiNi-SMA) distractor with different stretching force and different distance between two fixed ends on the height of alveolar ridge augmentation.Methods The mini distractors were all made of TiNi-SMAwire. The maximum stretching force and the distance between two fixed ends according to different distractors (A, B and C) were 20 mm, 700 g; 15 mm, 1 000 g; 20 mm, 1 000 g. 15 adultmongrel canineswere divid- ed into three groups randomly and extracted the mandibular premolars and first molar. One month later, box-shaped osteotomies of the alveolar bone were carried out in the left mandible and the TiNi-SMA distractors were buried. The bone height was measured and the radiographswere taken before and five weeks post operation continuously.Results One week post operation, the vertical ridge augmentation of group A, B and C averaged (7·55±1·02)mm, (4·97±0·34)mm, (8·54±0·82)mm and the height re- mained (7·20±1·05)mm, (4·93±0·21)mm, (8·04±0·78)mm five weeks post operation. There was no statistic difference in the height of alveolar ridge augmentation between Group A and C, but Group B showed significant difference with the other two groups. In each group, the height did not changed significantlywith the time. The radiographs showed obvious distraction gap post operation, and the new bone regenerated five weeks later.Conclusion It suggests that in the scope of suitable stretching force, the height of alveolar ridge augmentationwas determined by the size ofTiNi-SMAdistractor, that is to say, determined by the dis- tance between the two fixed ends.