The probability number distribution function of binary black hole mergers observed by LIGO/Virgo O3a has double peaks as a function of chirp mass $M_c$, total mass $M_t$, primary black hole mass $M_1$ and secondary one $M_2$, respectively. The larger chirp mass peak is at $M_c cong 30 M_{odot}$. The distribution of $M_2$ vs. $M_1$ follows the relation of $M_2cong 0.7M_1$. For initial mass functions of Population III stars in the form of $f(M) propto M^{-alpha}$, population synthesis numerical simulations with $0leq alpha leq 1.5$ are consistent with O3a data for $M_c gtrsim 20M_{odot}$. The distribution of $M_2$ vs. $M_1$ for simulation data also agrees with $M_2cong 0.7M_1$ relation of O3a data.