A projection position guiding method, adapted to a projection system, the projection system comprising a projection target, an image capturing device and a projector, and the projection position guiding method comprising: projecting a projection content to the projection target through the projector to generate a projection image, wherein the projection content comprises a plurality of positioning grid points arranged at intervals; capturing the projection target by the image capturing device to generate a captured image, wherein the captured image comprises at least a part of the projection image; and determining whether the plurality of positioning grid points satisfy a plurality of recognizable conditions according to the projection image in the captured image, wherein when it is determined that the plurality of positioning grid points comprise at least one unrecognizable grid point that does not satisfy at least one of the plurality of recognizable conditions, adjusting a color of the at least one unrecognizable grid point in the projection content; characterized in that before projecting the projection image to the projection target through the projector, the projector projects an initial projection content onto the projection target to generate an initial projection image, wherein the initial projection content comprises a plurality of initial positioning grid points arranged at intervals, and wherein the number of the plurality of initial positioning grid points of the initial projection content is less than the number of the positioning grid points of the projection content; the projection target is captured by the image capturing device to generate an initial captured image, wherein the initial captured image comprises at least a part of the initial projection image; it is determined whether the plurality of initial positioning grid points satisfy the plurality of recognizable conditions according to the initial projection image in the initial captured image; and when it is determined that the plurality of initial positioning grid points satisfy the plurality of recognizable conditions, performing said step of projecting the projection content onto the projection target. projecting a projection content to the projection target through the projector to generate a projection image, wherein the projection content comprises a plurality of positioning grid points arranged at intervals; capturing the projection target by the image capturing device to generate a captured image, wherein the captured image comprises at least a part of the projection image; and determining whether the plurality of positioning grid points satisfy a plurality of recognizable conditions according to the projection image in the captured image, wherein when it is determined that the plurality of positioning grid points comprise at least one unrecognizable grid point that does not satisfy at least one of the plurality of recognizable conditions, adjusting a color of the at least one unrecognizable grid point in the projection content; characterized in that before projecting the projection image to the projection target through the projector, the projector projects an initial projection content onto the projection target to generate an initial projection image, wherein the initial projection content comprises a plurality of initial positioning grid points arranged at intervals, and wherein the number of the plurality of initial positioning grid points of the initial projection content is less than the number of the positioning grid points of the projection content; the projection target is captured by the image capturing device to generate an initial captured image, wherein the initial captured image comprises at least a part of the initial projection image; it is determined whether the plurality of initial positioning grid points satisfy the plurality of recognizable conditions according to the initial projection image in the initial captured image; and when it is determined that the plurality of initial positioning grid points satisfy the plurality of recognizable conditions, performing said step of projecting the projection content onto the projection target.