The study of collision of ground-state ultracold polar molecules, in particular the collision properties of two-body exchange of non-reactive molecules, is of great significance for understanding the inelastic collision of molecules, for obtaining the molecular samples with long-lived, stable chemical properties and degenerate quantum states, and carrying out moleculesbased applications. Our previous work [Phys. Chem. Chem. Phys., 20, 4893 (2018)] has achieved the short-range photo-association preparation and optical dipole capture of 85Rb133Cs molecules in the lowest vibrational state, and have measured the inelastic collision coefficients of 85Rb133Cs with 85Rb and 133Cs atoms. However, the above works have not realized the research on the collision characteristics of molecules in rotational dynamics. In this paper, the collision characteristics of different rotational dynamics on the lowest vibrational state of 85Rb133Cs molecule have been studied. In particular, the population of rotational states in the ground state ultracold 85Rb133Cs molecules prepared by directly photoassociation was measured by loss spectroscopy. The transformation of population of rotational states in the ultracold 85Rb133Cs molecules was controlled by microwave pulse technique. The collision characteristics of pure and mixed states in the lowest vibrational ground state of ultracold 85Rb133Cs molecules were studied. The evolution of population of 85Rb133Cs molecules is measured in three cases of X1Σ+(v=0,J=1), X1Σ+(v=0,J=2) and the mixed state formed by the two rotational states. The rate equation is introduced to describe the molecular dynamics in the loss process and the molecular inelastic collision coefficient is obtained. The experimental results show that the collision coefficient of the rotational mixed state is higher than the pure rotational state, which is mainly caused by the dipole-dipole interaction between the neighboring rotational states. The work provides an important reference for understanding the inelastic collision mechanism of ultracold polar molecules and obtaining ultracold polar molecules at low temperature and high density.