Differential thermal analyses are performed on Mn-Si alloys with xSi = 0.6206 to 0.6364. Existence of a solid solution on the MnSix (with x around 0.63) phase is evidenced. Based on a careful review of the literature, the Mn-Si system is modeled using the Calphad method. The liquid, cbcc_a12, cub_a13, fcc_a1 and bcc_a2 phases are modeled as substitution solutions using the Redlich-Kister formalism. Mn3Si, Mn5Si3 and MnSi are treated as stoichiometric compounds and the stoichiometric variations of R-Mn6Si, nu-Mn9Si2 and MnSix are respectively described as (Mn)0.49(Mn,Si)0.36(Mn,Si,VA)0.15, (Mn)0.613(Mn,Si)0.215(Mn,Si)0.108(Si)0.064 and (Mn)0.146(Mn,VA)0.220(Mn,Si)0.244(Si)0.390. The results are in good agreement with the set of experimental data which is carefully selected. Finally, a few experimental data which could be checked are suggested.