Oral problems, especially dental caries and insufficient oral hygiene, have been still a concern world-wide sequel to tooth pain, discomfort, loss function and at most the harmful chronic impact of various oral infections, including pulpitis, periapical inflammation, periodontal disease which will due to loss of teeth if patients don’t treat impacted teeth, leading to crowding and malocclusion during and after mixed dentition. Screening of oral diseases should form a part of routine medical care in children. The caries prevalence was 70% and the mean dmft was 2.83 among 5 years old children who lives Khentii province (The national survey of oral health status of children and adults in Mongolia, 2013). The increase of dental caries incidence in low-economic countries is doubtless due to complicated causal web related to the economic, demographic and nutritional transitions, low tradition of oral health care, limited use of fluoride, and lack of oral health services (Peterson, 2003; Peterson et al., 2005; Sheiham, 1984). To assess caries prevalence and intensity among 7 years old children who were born in 2010. To calculate volume of treatment materials and costs after we determine such dental diseases as caries, pulpitis, periapical inflammation. This cross-sectional study included the 238 of 254 (116 girls, 122 boys) children who live in peri-urban area, Khentii province, and study first grade of Laboratory First school because our survey’s long term purpose was that we would treat all children who participated in this research. Two experienced dentists collected clinical oral health data. An intra-oral examination was conducted to assess dental caries in deciduous and permanent dentition. Dental caries prevalence evaluated using standard WHO oral survey methods. The prevalence of caries in the examined population was 83.61%. Caries intensity (dmft) was 4.84. The untreated caries index was 4.41. The counts of male participants were healthier than girl in category which is dmft index equals 0. But males had higher level of caries than females. The 18 first molars were impacted of caries. The 665 first molars were healthy. Even though we didn’t assess the malocclusion, which is anterior crowding of teeth, was observed almost all children. The high value of caries index was determined that indicate dental care and treatment for this age of children is not well provided. It is necessary to upgrade knowledge about oral health for both children and parents and caregivers and teaching constantly right way of tooth brushing methods. Then define whether they have habit that are brushing and flossing, children and parents don’t follow guidance. Dentists should train school doctors and health education teachers who contact to children closer than professional experts. In addition, to increase parental awareness of need for deciduous teeth treatment and for regular assessment of the status of newly erupted permanent teeth. This study can be translated into delivery of dental services to the community is essential.