A Brownian microscopic heat engine,driven by temperature difference and consisting of a Brownian particle moving in a sawtooth potential with an exteal load,is investigated.The heat flows,driven by both potential and kinetic energies,are taken into account.Based on the master equation,the expressions for efficiency and power output are derived analytically,and performance characteristic curves are plotted.It is shown that the heat flow via the kinetic energy of the particle decreases.The efficiency of the engine is enhanced,but the power output reduces as the α shape parameter of the sawtooth potential increases.The influence of the α shape parameter on efficiency and power output is then analyzed in detail.Like the Caot cycle,the Brownian heat engine can extract work from the temperature difference between heat reservoirs,where the Brownian working material operates as a transducer of thermal energy into mechanical work.In the last few decades,the study of Brownian heat engines has received considerable attention,not only for the construction of the miniaturized engine that helps us utilize energy resources at microscopic scales,but also for a better understanding of nonequilibrium statistical physics.[1-3] The thermodynamic properties of the Brownian heat engine have been explored intensively by considering different-model systems.