No, for purposes of calculating the earned income credit, child support isn't considered earned income.

Examples of items that aren't earned income include interest and dividends, pensions and annuities, Social Security and railroad retirement benefits (including disability benefits), alimony and child support, welfare benefits, workers' compensation benefits, unemployment compensation (insurance), nontaxable foster care payments, and veterans' benefits, including VA rehabilitation payments. Don't include any of these items in your earned income.