The prevalence of autism spectrum disorder in the world has increased over the last decade, but the prevalence, incidence, and characteristics of autism spectrum disorder in China were not well understood. Using administrative data, we aimed to estimate the prevalence and incidence of autism spectrum disorder and describe the co-occurring conditions in preschoolers in Beijing, China. The study focused on 0- to 6-year-old children with registered residence in Beijing, using cohorts derived from the Beijing Municipal Health Big Data and Policy Research Center. We conducted a detailed analysis of autism spectrum disorder prevalence among the cohorts, comparing estimates across 2 to 3 years for the same birth cohort (4 years, 5 years). For the 6-year-old cohort, we obtained 1-year prevalence estimates in 2021. Annual incidence rate was also calculated. The prevalence in 6-year-old children in 2021 was 10.5 per 1000 (95% confidence interval = 9.7--10.9). The male-to-female prevalence ratio was 4.3. Between 40% and 43% of preschool children had at least one co-occurring condition. The incidence for children 6 years old and under was 0.11% in 2019 and increased to 0.18% in 2021. Both the prevalence and incidence rates in Beijing were comparable to those reported in developed countries.