In order to improve the high‐density culture of microalgae, the traditional flat‐plate photobioreactors were modified with parallel baffles with different structures. The mixing characteristics of triphase flow in four types of bioreactors were investigated using the numerical simulation and experiments. The comparison shows that the results of simulations are consistent with those of experiments. The photobioreactor with ladder‐type parallel baffle could produce multiintensification functions of flow mixing, mass transfer, and bioreaction so that its integrated performances on high‐density culture are more prominent than other bioreactors. The culturing experiments were carried out in a bioreactor fed with air containing 10% CO2 at a flow rate of 10 L min−1. The results show that the growth rate of Chlorella vulgaris reaches 0.783 g L−1 d−1 with a total biomass of 7.21 g L−1 within 6 days, further achieving the efficient high‐density prolonged culture with multiperiods, which is significant for industrial applications.