The use of ethanol can be a solution for reducing of gasoline consumption and concentration of emissions in the agricultural SI engines. The engine performance changes when using a blended fuel. In this study, first, the effect of various bioethanol-gasoline blends at different loads and speeds was experimentally investigated. The brake thermal efficiency at all conditions decreases with increasing ethanol percentage, and that advanced spark timing provides a good opportunity to increase it. as well as concentrations of HC and CO increased while amount of CO2 and NOX are decreased compared to basic state. In the second stage, the effect of different advanced spark timings and the determination of the appropriate spark timing were carried out using GT-POWER. Brake thermal efficiency increases with appropriate spark advance and decreases with increasing engine speed. The maximum brake thermal efficiency was obtained with E10, E20, and E30 in 2500rpm as 27.02%, 27.03%, and 26.75%, respectively. Also, the positive and negative effects of adding ethanol to gasoline are nearly neutralized; therefore, the maximum brake thermal efficiency is almost identical. In the third part, the brake thermal efficiency and concentration of emissions with E30 and appropriate advanced spark timing (24BTDC) at a speed of 2500 rpm was experimentally investigated. The brake thermal efficiency increased from 25.01% to 27.37%. Also, the concentrations of HC and CO decreased, while the concentrations of CO2 and NOx increased and close to basic state (E30 & 20 BTDC), but concentrations of CO2 and NOx are less than pure gasoline state.