Abstract: Motivated by the goal of discovering more accurate characteristics of Chinese stock market,this paper investigates the powerlaw properties and criticality of the Shanghai Stock Exchange Compound Index (SSEECI) with two benchmarks of 5-min and 1-day database.We find that the center profile of returns distribution is well described by the Lévy regime and,more important,that the approximately syrmnetric tails of distribution are characterized by another power-law regime with an exponent well out of the Lévy range 0< a <2 and also beyond the exponent α≈3 of fully developed markets.Moreover,we also show that returns appear to exhibit the criticality.When timescale △t>4 days,the distribution exhibits the slow convergence to normal Gaussian behavior.The phenomena support that the critical timescale △t≈4days of fully developed markets is universal for Chinese stock market.

Key words: multiscale, powerlaw property, criticality, stock market