In a display system in an excavator, a position of an upper boundary line and a position of a lower boundary line are calculated. The upper boundary line indicates a height of a top of a cross section of a display object surface. The lower boundary line indicates a height of a bottom of the cross section of the display object surface. When the current position of the excavator is between the upper boundary line and the lower boundary line, a predetermined reference point of a display range is set to a predetermined position between the upper and lower boundary lines. When the current position of the excavator is above the upper boundary line, the reference point is set above the predetermined position. When the current position of the excavator is below the lower boundary line, the reference point is set below the predetermined position.