Butanol is deemed as the potential alternative fuel for future development, and the previous researches show poor injection spray atomization when high butanol concentration blended fuel applying on stock small scooter engines.In this research, a platform is built to observe the spray atomization phenomena with 2.5kg/cm2 (2.452bar) 、 3.5kg/cm2(3.433bar) injection pressures and various n-butanol volume percent concentration blended fuels, B60, B80 and B100. After that, engine experiments are undergone with above conditions under wide open throttle (WOT) with stoichiometric air fuel ratio (AFR) at 4000rpm. The experiment results are analyzed and discussed from different aspects eventually.Injection spray observation shows that worse spray atomization appears accompanied with higher concentration blended fuel. But when the injection pressure increases, higher shear force acting on the injection spray improves the breakup of fuel and enhances the effect of fuel spray atomization.The engine experimental results fuel spray with B80 and B100 blended fuel under 2.5 kg/cm2 result in poor performance due to much higher viscosity. But after rising up the injection pressure brings huge improvements performance. Also, the engine runs more steadily with smaller coefficient of variation (COV) of indicated mean effective pressure (IMEP) whenever better spray atomization can be realized by increased injection pressures. In addition, because of faster combustion speed introduced by fully mixed air fuel mixture, shorter period of mass fraction burned (MFB) and higher heat release rate (HRR), which represent better engine performance.