An intensive multifunctional fully variable valve actuation system for a 4-cylinder internal combustion engine belongs to the field of valve actuation systems of internal combustion engines and comprises oil feeders, a cycle selector, a mode converter, two-position three-way valves, a two-position two-way valve, an valve actuator and the like. The cycle selector only needs the two oil feeders, the two two-position three-way valves and one two-position two-way valve to achieve a variable valve event required by an actuating mode and a braking mode of the internal combustion mode, so that powerful functions are achieved through extremely low costs; the operation of the valve is completely flexible, particularly the closing process of the valve is not restricted by the operation phase of the oil feeders, a valve advanced closing event required by idling and middle-low loads of the internal combustion engine is met, and fuel consumption and emission of the internal combustion engine in practical application can be reduced sufficiently; the intensive multifunctional fully variable valve actuation system for the 4-cylinder internal combustion engine can be applied to a naturally aspirated and turbocharged internal combustion engines only by exchanging objects communicated onto the two oil openings of the mode converter, the type adaptability is good, the application range is wide and the arrangement of the system on a practical vehicle type can be facilitated.