During recent years the increasing consumption of fossil fuel has led to the search for alternative energy. Microalgae emerged as one of the potential sources of Bio-fuels from algae, and it is mostly preferred because it is sustainable and environment-friendly. The oil extracted from spirulina and chlorella microalgae through pyrolysis process at a temperature of 350oC, and the bio-oil properties were analysed. When compared to spirulina bio-oil, the viscosity and density of chlorella bio-oil were very close to the conventional diesel fuel. The Experiment was conducted in a single cylinder four stroke diesel engine for various loading conditions and was carried out for B10 blend for spirulina and chlorella algae bio-fuel, CL10D90 showed maximum output power at 100% load condition has been nearly same for diesel fuel than SP10D90, and the Specific fuel consumption is nearly same when compared with diesel. The Brake thermal efficiency of CL10D90 increases by 4% than SP10 D90 and 2% than diesel, and the combustion characteristic of peak heat release rate is higher and also there is a reduction in HC, CO emission at full load, with slight increase in NOX emission. The experimental result shows that the use of CL10D90 bio-oil in diesel engine is a suitable alternative to diesel.