Method of ensuring interior net storey height

The invention relates to a method of ensuring interior net storey height. The method comprises the steps: snapping a 1 m horizontal line on a building, and measuring a distance a1 from the 1 m line on the building to the bottom of a plate; calculating a standard distance b from the 1 m line on the building to the bottom of the plate; calculating a distance deviation c1; adjusting a distance d1 from the 1 m line on the building to a floor; according to the adjusted distance d1, calculating a standard distance b1 from the 1 m line on the building to the bottom of the plate; snapping an allowable deviation control line; snapping an adjacent point range control line; spanning a diagonal range control line; polishing and repairing the bottom of the plate; plastering a ceiling; checking flatness of the ceiling; and casting the floor. A ceiling flatness measuring tool comprises a hollow aluminum strip and a thin-walled aluminum tube. One end of the thin-walled aluminum tube is connected with the middle of the hollow aluminum strip. The hollow aluminum strip and the thin-walled aluminum tube are perpendicular to each other. By adjusting floor elevation properly and snapping the allowable deviation control line and range control lines to control plastering thickness of the ceiling, control precision of the interior net storey height is improved, thereby ensuring that the interior net storey height is accepted by one inspection.