The injection characteristics of biodiesel BD100 and blended fuel BD70, BD30 were studied. The effects of injection pressure and blend ratio on injection rate, cycle injection quantity and cycle-by-cycle variation were investigated. The results show that the injections of BD100, BD70 and BD30 start at the same time. With the decrease of biodiesel percentage, the injection duration is prolonged significantly, and the injection ends later. With the increase of injection pressure, the injection rate rising slope at the initial injection stage and the injection rate dropping slope at the end stage increase, both the peak injection rate during the stable injection stage and cycle injection quantity increase. The difference between the maximum injection quantity and the minimum injection quantity of BD100 is mainly caused by the injection rate fluctuation during the stable injection stage. The difference between the maximum injection quantity and the minimum injection quantity of blended fuel is mainly caused by the different injection duration of each cycle and the injection rate fluctuation during the stable injection stage, especially for BD30. With the decrease of biodiesel percentage, the cycle-by-cycle variation of BD100, BD70, and BD30 increases gradually.