The effects of exhaust pipe insulation on unregulated emissions of a spark ignition (SI) engine fueled with M10 (10% of methanol in blend by volume) and E10 (10% of ethanol in blend by volume) blends respectively were experimentally investigated with gas chromatography (equipped with a pulsed discharge helium ionization detector, PDHID). Experimental results show that methanol and ethanol emissions decreased after exhaust pipe heat insulation. After exhaust pipe heat insulation designed, aldehyde emissions did not change obviously at low engine load conditions (Tc<850K), but aldehyde emissions decreased significantly at middle-high engine load conditions (Tc≥850K), and the decreasing range of unregulated emissions increased with exhaust temperature rising. It is conducive to the oxidation of unregulated emissions with prolonging the reaction time of unregulated emissions in high temperature environment after exhaust pipe heat insulation designed. Unregulated emissions decreased significantly with exhaust pipe heat insulation when the exhaust temperature (Tc) was higher than about 900K. Exhaust temperature and reaction time had a greater influence on the oxidation of alcohol and aldehyde emissions.