In the paper, the finite-time stability control problem for the Lorenz chaos system is studied. Considering the existence of uncertainty and nonlinearity in the Lorenz chaos system, a control method is proposed, which makes the controlled Lorenz system achieve approximate finite-time stability. And one kind of extended state observer is improved and designed to solve the unknown problem of uncertainty and nonlinearity for the controlled Lorenz system. The approximate finite-time stability of the closed-loop system is analysed by introducing the singular perturbation theary. Simulation results show the effectiveness of the control method and observer.