The invention discloses a high-efficiency and multi-combustion-mode engine combustion system. A gas distribution mechanism in the system is a full-variable valve mechanism, and according to differentdegrees of negative valve overlap angles (NVO) provided by a full-variable valve, different combustion modes from HCCI, SACI to SI can be realized; and because of the effect of a pre-combustion chamber, an ignition position of a spark plug and propagation of an initial ignition core can be always ensured to be close to the stoichiometric ratio. In this way, a combustion process of main combustionchamber lean burn and pre-combustion chamber equivalence can be realized. In addition, when thermodynamic state in the cylinder is insufficient to achieve the HCCI, flame acceleration from a jet flamehole of the pre-combustion chamber can realize secondary heating and pressurization on the unburned mixed gas in the main combustion chamber, spontaneous combustion of the unburned gas is induced, sothat the SACI combustion mode can be more stably realized. Even though combustion is completely the SI combustion, fuel consumption can be obviously reduced by the acceleration effect of the jet holeon flame.