With the development of ultrafast science and attosecond laser technology, the pump-probe system based on isolated attosecond laser pulses is a key for attosecond science, which will be used to study electronic dynamics in attosecond time-scale. To obtain stable and reliable signals, it is necessary to ensure ultra-stable and ultra-accurate synchronization. Any timing jitter can cause signal disperse or get buried in noise, making it impossible to obtain the true physical mechanism. Based on above, the delay between pump and probe laser pulses must be controlled with an attosecond time resolution. In this work, a dual-layer system was developed to make a high-precision synchronization locking. To ensure that both layers have the same time jitter, we design an adapter to hold the elements, which are placed in the mounting. Timing jitter is obtained by shaking interference fringes through fast Fourier transformation, which can be calculated in several milliseconds. Then error signals are fed back to the PZT stage for compensation of real-time optical path drift. With such a design, a time-delay accuracy of 7.64 as to 15.53 as are realized, which is linearly related to the interferometer arm length from 1 m to 5 m and the R-square is 0.96. Moreover, the error between the experimental result of arm length of 8,10 meters and the result fitted with the above data is less than 3 as. These results shows that using a small interferometer can achieve fast detection of the time-delay accuracy of long-arm attosecond pump-probe detection systems in large scientific instruments, which is of important guiding significance for applications such as non-collinear attosecond streaking spectroscopy, time-resolved photoelectron spectroscopy, coherent synthesis, and other applications.