A variable orifice fuel injector comprising: (i) a nozzle body comprising passages for fuels, an inner cylindrical bore for receiving two longitudinally displaceable coaxial needle valves (1, 2), one is outward opening needle valve and another is inward opening needle valve, at least one group of fuel injection outlets (301, 309) in said nozzle body, at least one spring (5, 5') which urges said needle valves (1, 2) into biased seating positions to block fuels, and a valve block to hold control valves and having fuel inlets which can be connected to two pressured fuel reservoirs (12, 13), pressure control chambers (382, 125) which can press and release needle valves through connecting to pressurized and de-pressurized fuels, and (ii) said outward opening needle valve, has an opening position which is moving away relative to a nozzle body large end to inject fuel from at least one pressurized fuel reservoir through an annular fuel outlet and fuel injection outlets, and a seating position to block fuel flow, and (iii) said inward opening needle valve, which is fully contained in the said nozzle body, has an opening position by moving toward said nozzle body large end to connects at least one pressurized fuel reservoir and fuel injection outlets (309, 301) to inject fuel, wherein the lifting of said inward opening needle valve is independent of the position of said outward opening needle valve, and, has a seating position being in contact with a sealing surface of nozzle body to block fuel flow from fuel inlets to fuel injection outlets, a sealing surface at seating position is up stream of injection outlets, and (iv) characterized in that the said outward opening needle valve is partially contained in said inward opening needle valve and has a biased siting position on said inward opening needle valve, wherein the lifting of outward opening needle valve is independent of the position of said inward opening needle valve, wherein it is comprising at least two control valves (9, 10) to block or connect at least one type of fuel from high pressure fuel reservoirs (13, 12, 15') to low pressure fuel sink to produce the lifting and closing forces on said inward opening and outward opening needle valves (1, 2) through generating pressure differences in pressure control chambers (382, 125). (i) a nozzle body comprising passages for fuels, an inner cylindrical bore for receiving two longitudinally displaceable coaxial needle valves (1, 2), one is outward opening needle valve and another is inward opening needle valve, at least one group of fuel injection outlets (301, 309) in said nozzle body, at least one spring (5, 5') which urges said needle valves (1, 2) into biased seating positions to block fuels, and a valve block to hold control valves and having fuel inlets which can be connected to two pressured fuel reservoirs (12, 13), pressure control chambers (382, 125) which can press and release needle valves through connecting to pressurized and de-pressurized fuels, and (ii) said outward opening needle valve, has an opening position which is moving away relative to a nozzle body large end to inject fuel from at least one pressurized fuel reservoir through an annular fuel outlet and fuel injection outlets, and a seating position to block fuel flow, and (iii) said inward opening needle valve, which is fully contained in the said nozzle body, has an opening position by moving toward said nozzle body large end to connects at least one pressurized fuel reservoir and fuel injection outlets (309, 301) to inject fuel, wherein the lifting of said inward opening needle valve is independent of the position of said outward opening needle valve, and, has a seating position being in contact with a sealing surface of nozzle body to block fuel flow from fuel inlets to fuel injection outlets, a sealing surface at seating position is up stream of injection outlets, and (iv) characterized in that the said outward opening needle valve is partially contained in said inward opening needle valve and has a biased siting position on said inward opening needle valve, wherein the lifting of outward opening needle valve is independent of the position of said inward opening needle valve, wherein it is comprising at least two control valves (9, 10) to block or connect at least one type of fuel from high pressure fuel reservoirs (13, 12, 15') to low pressure fuel sink to produce the lifting and closing forces on said inward opening and outward opening needle valves (1, 2) through generating pressure differences in pressure control chambers (382, 125).