Due to the requirement of disassemble for existing sky screen position detection method in flying projectile, a novel position detection method was proposed without dismantling the flying projectile. At first, the theodolite was used to build the datum plane. In the second, by using the specified stroboflash tiny illuminant and setting the output threshold of sky screen, based on the relative displacement distance between the transition table and the datum plane while the output signal of illuminant was showing on the sky screen, the relative position parameters were detected. Finally, when the sky screen tilted 2,-2 and -5,the error of measured tilted angle and actual angle was always less than 1, the experiment results showed that the detection accuracy was more than 1 which agreed with the theoretical analysis. The proposed method does not require the disassemble of the flying projectile, it saves the time and can be further used in the position measurement of fly projectile.