Based on monthly data of dual-listed companies in A share and H share markets from November 2006 to November 2009, this paper provides an explanation for A-H share premium by introducing two behavioral factors: heterogeneous beliefs and investor sentiment. The results show that, under the short-sales constraints of A share market, the stronger the heterogeneous beliefs, the higher the A-H premium rate.The higher the investor sentiment of A share market, the higher the A-H premium rate. Under higher investor sentiment, A shares of stocks whose intrinsic value is difficult to estimate are more likely to be overpriced, leading to a higher A-H premium rate. Moreover, higher investor sentiment can strengthen the effect of heterogeneous beliefs on A-H premium rate. Overall, theories on heterogeneous beliefs and investor sentiment can well explain the irrational phenomenon of A-H share premium.