In this paper, we conduct the experiment and simulation on 31D _5/2+6S _1/2( F= 4) Cs ₂ultralong-range Rydberg molecules (ULRMs). These molecules are prepared by employing a two-photon photoassociation scheme. Two distinct ultralong-range Rydberg molecular signals are observed at the detuning –162.8 MHz and –66.6 MHz of 31D _5/2atomic resonant line, which are bound by the pure triplet potential and mixed singlet-triplet potential, respectively. We use the model of scattering interaction between the Rydberg electron and ground-state atom to perform the simulation. The molecular potential-energy curves are obtained by solving the Hamiltonian on a grid of intermolecular distances R. The calculations of the binding energy of pure triplet and mixed singlet-triplet v= 0 vibrational states are compared with the experimental measurements. The calculated and measured values of the binding energy are in good agreement. The s-wave pure triplet and singlet zero-energy scattering length are obtained to be ${a}_{{\rm{s}}}^{{\rm{T}}}({0})=-{19.16}{a}_{0}$ and $ {a}_{{\rm{s}}}^{{\rm{S}}}(0)=-{1.92}{a}_{0} $ , respectively. This kind of molecule with large size, abundant vibrational states and large permanent electric dipole moment is an excellent candidate for studying low-energy collision dynamics. The study of these molecules will further deepen and enrich the understanding of the special binding mechanism and exotic properties of the ULRMs.