In this paper, we studiy the Feynman's ratchet and pawl heat engine in a one-dimensional lattice. The dynamics of the particle is described by a master equation. The expressions of the current, efficiency and power output of the heat engine are derived analytically. The influences of the height of barrier, external load force and the temperature ratio of the heat reservoirs on the efficiency of heat engine are discussed. When the steady-state current is zero, there is a nonzero heat flux transterred from the hot bath to the cold bath, which is similar to the heat leak of the irreversible Carnot model. The curve of the power output versus the efficiency is a loop-shaped one. The heat engine is irreversible and the efficiency is less than the Carnot efficiency. The heat engine can work in optimal operation by optimizing the performance parameters of the heat engine.