A system for controlling fuel supply to an engine for ships, comprising: a system operating zone provided with a high pressure pump configured to pump LNG and a gasifier which gasifies the LNG pumped by the high pressure pump; a supply operating zone provided with a supply line for supplying the LNG gasified by the gasifier to the engine; a first shut-off valve disposed downstream of the gasifier in the system operating zone; a second shut-off valve disposed in the supply operating zone and upstream of a point where a vent line is branched from the supply line, the first and second shut-off valves dividing the system operating zone and the supply operating zone from each other, thereby allowing the system to be controlled such that each of the operating zones can be set to have a different preset pressure; a main gas valve installed on the supply line upstream the engine, the vent line being branched from the supply line at an upstream side of the main gas valve; a first pressure detection unit configured to detect a first pressure of LNG in the system operating zone at a downstream side of the gasifier, between the first shut-off valve and the second shut-off valve; a second pressure detection unit configured to detect a second pressure of LNG in the supply operating zone upstream the engine and at a downstream side of the main gas valve; a return line provided with a recirculation valve configured to return at least part of the pumped LNG from the high pressure pump to an LNG storage tank or an upstream side of the high pressure pump; a pressure regulation valve installed on the vent line; a first controller configured to receive the first pressure value detected by the first pressure detection unit and to control a degree of opening of the recirculation valve and a speed of the high pressure pump depending upon the detected first pressure value with respect to a preset pressure of the system operating zone to control the pressure of LNG in the system operating zone; a second controller configured to receive the second pressure value detected by the second pressure detection unit and to control opening or closing of the main gas valve and the pressure regulation valve depending upon the detected second pressure value with respect to a preset pressure of the supply operating zone to control the pressure of LNG in the supply operating zone, the preset pressure of the supply operating zone being set to a required supply pressure according to load of the engine; wherein the system is configured such that the preset pressure of LNG in the system operating zone is set to be higher than that of LNG in the supply operating zone. a system operating zone provided with a high pressure pump configured to pump LNG and a gasifier which gasifies the LNG pumped by the high pressure pump; a supply operating zone provided with a supply line for supplying the LNG gasified by the gasifier to the engine; a first shut-off valve disposed downstream of the gasifier in the system operating zone; a second shut-off valve disposed in the supply operating zone and upstream of a point where a vent line is branched from the supply line, the first and second shut-off valves dividing the system operating zone and the supply operating zone from each other, thereby allowing the system to be controlled such that each of the operating zones can be set to have a different preset pressure; a main gas valve installed on the supply line upstream the engine, the vent line being branched from the supply line at an upstream side of the main gas valve; a first pressure detection unit configured to detect a first pressure of LNG in the system operating zone at a downstream side of the gasifier, between the first shut-off valve and the second shut-off valve; a second pressure detection unit configured to detect a second pressure of LNG in the supply operating zone upstream the engine and at a downstream side of the main gas valve; a return line provided with a recirculation valve configured to return at least part of the pumped LNG from the high pressure pump to an LNG storage tank or an upstream side of the high pressure pump; a pressure regulation valve installed on the vent line; a first controller configured to receive the first pressure value detected by the first pressure detection unit and to control a degree of opening of the recirculation valve and a speed of the high pressure pump depending upon the detected first pressure value with respect to a preset pressure of the system operating zone to control the pressure of LNG in the system operating zone; a second controller configured to receive the second pressure value detected by the second pressure detection unit and to control opening or closing of the main gas valve and the pressure regulation valve depending upon the detected second pressure value with respect to a preset pressure of the supply operating zone to control the pressure of LNG in the supply operating zone, the preset pressure of the supply operating zone being set to a required supply pressure according to load of the engine; wherein the system is configured such that the preset pressure of LNG in the system operating zone is set to be higher than that of LNG in the supply operating zone.