In cross-clock data transmission, metastable phenomena often occur due to violation of the setup time and hold time of flip-flops, resulting in bit error. In order to observe the metastable process directly, it uses the metastable observation platform to test the bit error of TTL block holding integrated edge flip-flop 74LS74 chip and CMOS transmission gate integrated edge flip-flop 74HC74 chip in setup time domain. Test results show that the performance of the two chips is close, and there is a 0%~100% BER transition band in the setup time of 0.9~1.6ns, in which the visual waveform of metastable process can be observed. It is found that there is a stable monotonic variation curve of BER in the above range when the input level of trigger jumps up. When the input level of the flip-flop jumps down, the BER changes from 0% to 100% instantaneously, and the transition zone cannot be observed. When the input jumps down and the delay parameter increases or decreases in one direction, the transient region will be different and presents a backlash phenomenon.