This study represents the analysis of smoke of biodiesel by using smoke tester. In this article biodiesel is taken as a fuel instead of diesel and quantity of emitted pollutants HC and CO is evaluated by taking different quantity of biodiesel at different load. Biodiesel is a diesel fuel that is made by reacting vegetable oil (cooking oil) with other common chemicals. Soybean oil is currently a major feedstock for production of biodiesel. The most common method of biodiesel production is a reaction of vegetable oils or animal fats with methanol or ethanol in the presence of sodium hydroxide (which acts as a catalyst). The transesterification reaction yields methyl or ethyl esters (biodiesel) and a byproduct of glycerin. Biodiesel is not straight vegetable oil burned in a diesel engine. Biodiesel has better lubricating properties and much higher cetane rating than today's low sulfur diesel fuels. Biodiesel addition reduces fuel system wear and in low levels in high pressure systems increases the life of the fuel injection equipment that relies on the fuel for its lubrication. Biodiesel may be used in any diesel automotive engine in its pure form or blended with petroleum-based diesel. No modifications are required, and the result is a less-expensive, renewable, clean-burning fuel. This work shows how use of biodiesel will affect the emission of pollutants. Diesel Engine is compression ignition engine and use diesel as fuel, in this engine alternative fuel can be used. One alternate fuel is biodiesel. Biodiesel can be used in pure form or may be blended with petroleum diesel at any concentration in most injection pump diesel engines and also can be used in Vehicle, Railway, and Aircraft as heating oil.