The objective of this study is to investigate the effect of biodiesel blending on spray and combustion characteristics. In order to do this, blended fuels containing 0, 5, 20, 50, 100% biodiesel based on weight fraction are injected through common rail into constant volume combustion chamber. In the non-evaporating spray experiment, macroscopic spray images are acquired by shadowgraphy using the light source and high speed camera. Spray images are analyzed by numerical code which adjusts brightness, gives threshold and measures the macroscopic properties of spray. Also, microscope is used for taking images of droplet at three different locations of spray. And then, Sauter mean diameter (SMD) of droplets is calculated after image analysis. In the combustion experiment, hydrogen gas premixed with dry air is used for making diesel combustion condition of high pressure and temperature. Inner pressure is measured and heat release rate, ignition delay and full combustion time are calculated from the pressure data. As a result, spray cone angle decreased because of the higher density and dynamic viscosity of biodiesel which can make friction in the body of the liquid and at the boundary between the liquid and its containing walls, however, it does not seemed that spray penetration was affected by these factors considerably. SMD increased in accordance with increment of biodiesel blending ratio due to the same reasons of spray cone angle. it seems that higher viscosity of biodiesel makes liquid jets hard to break and causes coalescence of droplets. In the combustion experiment, ignition delay of biodiesel was shorter than diesel due to higher cetane number. And the peak value of heat release rate increased and the end of combustion was advanced owing to higher combustion efficiency cause by the characteristic of oxygenated fuel. Also, there is a little probability of micro explosion in blended fuel which can make better quality of atomization.