The invention relates to a labeled graph used for a projection interaction system and a calibration detection method thereof. Compared to the prior art, by using the labeled graph and the method of the invention, a defect that the labeled graph and the calibration method are easy to be interfered by extraneous illumination is overcome. A grid set comprises 49 grids with a same size, wherein the 49 grids are formed through intersecting 8 transverse drawn lines and 8 vertical drawn lines. Types of the grids are main grids and auxiliary grids. The main grids are the grids whose internal portions are provided with oblique lines. The auxiliary grids are grids whose internal portions are blank. One auxiliary grid is arranged between the adjacent main grids in the grid set. There are 16 main grids and 33 auxiliary grids. By using the labeled graph and the method of the invention, the interference of the extraneous illumination is overcome, a calibration success rate is increased and calibration time is saved.