We examined the association of socioeconomic status with the diagnosis of autism during 16--30 months of age. Using data from a national survey in China, we included 6049 children (55.6% male) in the final analysis, among which 71 of them were clinically diagnosed with autism. Adjusted for covariates, the odds ratios for having the diagnosis of autism (2.46, 95% confidence interval: [1.32, 4.59]) among children whose mother's level is "junior middle school or below" were significantly higher than children whose mother's level is "college or above." Among children of lower educated mothers, there is a higher risk of being diagnosed with autism at a young age. We recommend more support for families with a low socioeconomic status to early detect, diagnose, and manage autism.