Biodiesel is a clean and renewable energy that its use as a suitable substitute for diesel fuel is spreading in all around the world. Biodiesel can be used as pure or mixed with diesel fuel. In this research safflower seed was considered as a suitable raw material and after the extraction of oil and transesterification reaction the physical and chemical characterization of biodiesel and its 20 percent mixture with diesel fuels was studied using standard test. Our study shows that the 20 percent mixture gives the best result compared with pure safflower biodiesel and fuel, and all its specifications were in standard ranges defined in EN 14214, ASTM D6751.