To study the chemical effect of direct current arc plasma igniter, the emission spectrum of plasma jet was measured, and the active particles produced by the interaction of plasma jet with atmospheric air were analyzed. The NO and CO volume fractions were measured quantificationally by smoke analyzer at the 8cm downstream the plasma igniter exit, and the changing law between arc current and NO, CO volume fractions was obtained. The results show that the plasma jet interacting with atmospheric air produced active particles (H, O, N), charged particles(O2+, N2+), and excited particles(N2(A3), N2(B3), N2(C3), N2(a1), O2(a1), O2(b1)). The NO and CO volume fractions increased with rising of arc current and feedstock argon flow rate.