A method for controlling a plug-in hybrid electric vehicle , comprising: setting, by a controller , an initial distance until charge (DUC); calculating, by the controller , a current DUC by subtracting a travel distance of the plug-in hybrid electric vehicle from the initial DUC after the initial DUC is set; calculating, by the controller , a current distance to empty (DTE) based on a current state of charge (SOC) of a battery ; comparing, by the controller , the current SOC of the battery with a reference SOC; comparing, by the controller , the current DUC with the current DTE when the current SOC is greater than the reference SOC; determining, by the controller , whether a high speed condition or a high load condition is satisfied when the current DUC is greater than the current DTE; setting, by the controller , a driving mode of the plug-in hybrid electric vehicle to be a charge sustaining (CS) mode when the high speed condition or the high load condition is satisfied; characterized in that the method further comprises the following steps: comparing, by the controller , demand power of a driver with a first predetermined power when the driving mode of the plug-in hybrid electric vehicle is set to be the CS mode; starting, by the controller , an engine when the demand power of the driver is greater than the first predetermined power; and comparing, by the controller , the demand power of the driver with a second predetermined power when the driving mode of the plug-in hybrid electric vehicle is set to be a charge depleting (CD) mode; and starting, by the controller , the engine when the demand power of the driver is greater than the second predetermined power, wherein the first predetermined power is less than the second predetermined power. setting, by a controller , an initial distance until charge (DUC); calculating, by the controller , a current DUC by subtracting a travel distance of the plug-in hybrid electric vehicle from the initial DUC after the initial DUC is set; calculating, by the controller , a current distance to empty (DTE) based on a current state of charge (SOC) of a battery ; comparing, by the controller , the current SOC of the battery with a reference SOC; comparing, by the controller , the current DUC with the current DTE when the current SOC is greater than the reference SOC; determining, by the controller , whether a high speed condition or a high load condition is satisfied when the current DUC is greater than the current DTE; setting, by the controller , a driving mode of the plug-in hybrid electric vehicle to be a charge sustaining (CS) mode when the high speed condition or the high load condition is satisfied; characterized in that the method further comprises the following steps: comparing, by the controller , demand power of a driver with a first predetermined power when the driving mode of the plug-in hybrid electric vehicle is set to be the CS mode; starting, by the controller , an engine when the demand power of the driver is greater than the first predetermined power; and comparing, by the controller , the demand power of the driver with a second predetermined power when the driving mode of the plug-in hybrid electric vehicle is set to be a charge depleting (CD) mode; and starting, by the controller , the engine when the demand power of the driver is greater than the second predetermined power, wherein the first predetermined power is less than the second predetermined power. <EOS>