BACKGROUND. The measurement of oral health is recognized as a critical feature of numerous dental activities: describing normal biologic processes, understanding the natural history of disease, testing hypotheses regarding preventive agents, and planning and evaluation of health services. In modern times, statistical methods are widely being used to describe the probability of caries formation by calculating the progress and progression of dental caries for each individual by means of investigational correlations to detect and control risk factors for dental caries and periodontal diseases. OBJECTIVE. The purpose of this study is to identify the correlation between the incidences of dental caries (DMFT) and its influencing risk factors for Mongolians in order to establish the fundamental criteria for oral health index. MATERIAL AND METHODS. Data were collected from 240 volunteers in six different age groups by using a questionnaire and an intra oral examination combined with laboratory tests. The oral health index is divided into 5 major categorical factors including the residual number of natural tooth, caries state, periodontal state, other oral health state and oral health management habits and systemic condition that determines the relationship between the incidences of dental caries and influencing risk factor for each item. RESULTS. Significantly different results were observed for Mongolian people in terms of prevalence and proportion of oral disease and oral state which led to the establishment of criteria for oral health index by statistical significance factors in all age groups (p <0.05). CONCLUSION. It is possible to create and introduce a scoring system of individual oral health index that could be applied to the evaluation oral health program that is suitable for calculating future illnesses and prognosis of oral diseases.