Abstract: This paper puts emphasis on discussing the performance analysis for detection model of frame synchronous codes under the stable comdition of bits synchronization. In the space digit communication, we often adopt the detection model with both fixed correlation and maximum correlation level criterions. Here, we calculate the detection probability, set up the state model of detection process and deduces the equation of estimating, synchronous detection time. Hence, it provides scientific basis to performance analysis, for the two detection devices and profits selecting the parameter for the frame synchronous detection devices.