The kinetics and mechanism of the gas-phase reactions between hydroxy methyl radical (CH2OH) or methoxy radical (CH3O) with hydroproxy radical,(HO2) have been theoretically investigated on their lowest singlet and triplet suffices. Our investigations indicate the presence of one deep potential well on the singlet surface of each of these systems that play crucial roles on their kinetics. We have shown that the major products of CH2OH + HO2 system are HCOOH, H2O, H2O2, and CH2O and for CH3O + HO2 system are CH3OH and O. Multichannel RRKM-TST calculations have been carried out to calculate the individual rate constants for those channels proceed through the formation of activated adducts on the singlet surfaces. The rate constants for direct hydrogen abstraction reactions on the singlet and triplet surfaces were calculated by means of direct-dynamics canonical variational transition-state theory with small curvature approximation for the tunneling.