We can expand the variational space by optimize two site at a time to enhance the ability of escape the local minima. In this article, the mixed-precision scheme of this two-site DMRG method is discussed. The tensor lattice of the two-site DMRG method is presented in Fig. . Conventionally, ab-initio quantum chemistry software apply the double precision as default standard. This double precision sweep can be represented with a simplified lattice form in Fig. . The detailed work flow of the double precision two-site DMRG algorithm is presented as Algorithm 1. The operations within each sweep step is presented in Algorithm 2.