Based on the PEMS on-board emission testing method, burning with the pure national Ⅳ diesel, 10% and 20% by volume butanol-diesel blends on a diesel PCV, the experiment equipped with an on-board gas emission testing system which made in Horiba of Japan. Comparing with the three different kinds of fuels’ emission in different kinds of roads type, referring to the different emission in different working conditions, the characteristic of the on-road gas emission from a diesel PCV with butanol-diesel blends have been analyzed. The result shows that, a diesel PCV burning with the butanol-diesel blends can reduce the CO emission obviously, especially on the medium-high-velocity working condition; the THC emission increases with the increasing of the butanol concentration; the CO2 emission basically unchanged,; the NOX emission changed a little because of the influence with the working condition and the engine parameters.