Pre-chamber ignition systems are considered as an effective technique to achieve an ultra-lean burn combustion. Hot combustion products and flames generated from pre-chamber combustion create high-speed turbulent jets, which ignite an ultra-lean mixture in the main chamber. This turbulent ignition can be classified as a jet and flame ignition process with thermal and chemical kinetic effects imposed on the main chamber by the pre-chamber. The purpose of this paper is to investigate the chemical effects of pre-chamber combustion products on main chamber ignition performance over a range of operating conditions in pre-chamber. A zero-dimensional pre-chamber combustion model was developed using CHEMKIN-PRO software. By varying the equivalence ratio of reactants, simulation results indicated that the pre-chamber generated more active radicals when burning around stoichiometric conditions but more low-carbon species when burning in rich conditions. Therefore, rapid ignition performance was observed in the ultra-lean mixture of main chamber with additional combustion products from the pre-chamber burning with a stoichiometric mixture. This contributed to the transfer of highly active species especially OH radicals from pre-chamber into main chamber. Heat release rate and laminar flame speed are promoted with combustion products from pre-chamber burning with a relatively rich mixture. The related reaction and species sensitivity analysis were also conducted to explain the above findings.