Preschool children aged 3-6 years are vulnerable to exposed to particulate matter ("PM10" and "PM2.5"). It is required in evaluating the risk based on dose of preschool children. Microenvironments which preschool children mainly visited were classified. Inhalation type was adapted in each microenvironment in consideration of intensity of activity. The exposure scenario was described as preschool children had been living in Seoul, South Korea, and dose was calculated by considering time-activity-pattern with major microenvironments and inhalation type of preschool children for 24 h. Monte-Carlo simulation technique is used to estimate dose of particulate matter in probabilistic distribution by age and sex. The contribution of exposure by microenvironments and inhalation type was calculated. Risk assessment was performed based on WHO interim target-3 24-h concentration in order to estimate. Sensitivity analysis was performed to determine the effective variable of dose. As a result of the study, the dose of PM was higher for boys than girls and tended to decrease with age. The overall contributions of PM doses by microenvironments were daycare center, home, other facilities, transit, and outdoors, respectively, although differed between daycare center and home priority by age and sex. Especially, the contribution of daycare center and home was very high, accounting over 85% of the total. The overall contributions of PM doses by inhalation type were "run," "stable," "sleep," and "walk inhalation," respectively. The results of hazard quotient showed that "PM10" exceeded the WHO interim target-3 24-h concentration standard by about 10% and "PM2.5" exceeded about half. Through sensitivity analysis, PM concentration was confirmed as a major influence variable for doses. This study was able to affirm the overall exposure status of "PM10" and "PM2.5" for preschool children, and this is expected to be used in regulation and public health. © 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.