This article reported 1 child patient with early-onset methylmalonic acidemia and proceeded gene detection for the child and his parents. The detecting results showed that there were respectively heterozygosis mutations of c.609G>A,p.(Trp203*) and c.567dupT,p.(Ile190Tyrfs*13) in the MMA CHC gene of child's parents, and all of the diseases were entailed to the child and caused the paroxysm of child. Consequently, the c.567dupT,p.(Ile190Tyrfs*13) was considered as a kind of new gene mutation. After being treated with vitamin B12 and levocamitine, the clinical symptoms and organic acid content of hematuresis of this child patient had taken a turn for the better.