Abstract We investigate the two loop electroweak corrections to B meson rare decays and in the minimal supersymmetry standard model (MSSM) extension with two triplets and one singlet (TNMSSM). The new particle contents and interactions in the TNMSSM can affect the theoretical predictions of the branching ratios and , and the corrections from two loop diagrams to the process can reach around . Considering the latest experimental measurements, the numerical results of and in the TNMSSM are presented and analyzed. The findings indicate that the results in the TNMSSM can fit the updated experimental data well, and the new parameters , clearly affect the theoretical predictions of and .