To evaluate the effects of progressive loading on implants placed into extraction sockets. 4 beagle dogs were extracted bilateral 3rd, 4th and 2nd premolar and immediately inserted the implant at first surgery (0d), 14d and 21d. Using the newly developed vertical occlusion loading system, progressive loading procedures were taken 24h after insertion. The vertical bone loss (VBL) and bone-to-implant contact ratio (BIC) was measured by image analysis software and analyzed using the paired student t test. After 28d period of healing, each animal was sacrificed and the samples were evaluated by scanning electron microscopy (SEM). The mean vertical bone loss in control groups was larger than that of the experimental groups at 14, 21 and 28 day (P<0.05). SEM showed that the mineralization rate of experimental groups was faster than the control groups. The bone-implant contact ratios in experimental groups were more than that in the control groups. The differences were statistically significant (P<0.05). Compared with non-loading implant, progressive loading can promote osseointegration and decrease vertical bone loss. Progressive loading of implants placed into extraction sockets can be performed without interfering with the osseointegration process.