Background:  Trauma, neoplasms, congenital defects, infections, open fractures, and failed arthroplasty can all cause bone defects. In contrast to other tissues, bones have the ability to regenerate and repair themselves; most of the time, fractures and injuries to the bones can heal without leaving scars. One of the biomaterials that has been proposed for use in conjunction with bone grafting is platelet-rich fibrin (PRF). To speed up bone regeneration, PRF can be applied alone or in combination with grafting material thus promotes angiogenesis, immunity and epithelial healing and soft tissue maturation processes. This osteogenesis process can be described by the quantity of osteoblasts which is comparable to the osteogenesis process. Meanwhile, Alkaline Phosphatase (ALP) is used as a matrix protein indicator that shows a rise in the activity and quantity of osteoblasts.Purpose: The objective of this study is to examine the way PRF affects the proportion of ALP and osteoblasts during bone-healing process in mice that have received autografts. Research able to show the effect of PRF in the bone healing process to accelerate bone healing so that it can be a reference for further research and also applied in medical practice, especially orthopedics to improve the quality of bone healing.Material and Methods: Fourteen male Rattus norvegicus samples, weighing between 450 and 600 grams and aged between 12 and 14 weeks, were used in the study. Two groups of mice were randomly selected, with seven in group P1 and seven in group P2. In both groups, general anesthesia was performed to collect PRF and autografts. PRF from the jugular vein was 2 ml from each animal. The autograft was taken from the cancellous bone of the right iliac crest. The defect was created in the distal right femur using a size 2.0 k-wire with a depth of 3 mm. Autologous cancellous bone from the iliac crest and extra PRF were subsequently used to fill the defect in accordance with the experimental animals' group. After 4 weeks of observation, euthanasia was carried out and the samples were stored in 10% formalin solution after which preparations and immunohistochemistry were taken. After obtaining the sample, the number and scoring of osteoblasts will be carried out, as well as the ALP presentation which will then be analyzed using statistical tests.Conclusion: Administration of PRF may increase the number of osteoblasts in the new bone formation process and in long bone defects in Rattus norvegicus using the autograft bone graft method. It also increase the formation of new bone tissue quicker in the new bone formation process and in long bone defect using the auto graft bonegraft method.