The lean combustion strategy can improve fuel efficiency and also reduce pollutant emission. As a forced ignition method, the precombustion chamber turbulent jet ignition technology can effectively improve combustion stability. The combustion characteristics of turbulent jet ignition in lean mixtures were studied by using numerical simulation. The results show that the maximum combustion pressure of turbulent jet ignition is 66.4% higher than that of traditional spark plug ignition, and the NO_x emission is 93.9% lower than that of equivalence ratio combustion when the excess air ratio (φ_a) of mixture is 1.5. Increasing the auxiliary fuel of the pre-combustion chamber can increase the initial kinetic energy of hot jet and improve the jet flame structure to accelerate the consumption rate of mixture in the main combustion chamber. In the turbulent jet ignition mode, the turbulent kinetic energy of main combustion chamber has two peaks, and the increase of turbulent kinetic energy promotes combustion.