This paper studies the herding behavior in the Chinese A and Hong Kong H stock markets during extreme market condition and different financial crisis periods. The results indicate that the A-share market exhibit significant herding behavior, in particular, herding strongly exists in the down market. When the turnover and negative bias of market are the extremely low, the herding behavior of A-share market is no significantly changed, however, H-share market exists significant herding behavior. Both A-share and H-share markets have significantly herding behavior during the extreme high volatility period. Finally, the herding behavior in the Chinese A stock market became stronger in US subprime mortgage crisis, slowed down in European debt crisis, and had no significantly change in Chinese credit crunch period.