Using the first-principles theorythe electronic structures and magnetic properties of S vacancies (VS) and Tc-doped monolayer MoS2 were investigated. Results reveal that the Tc-doped monolayer MoS2 is a n-type semiconductor with ferromagnetism. Compared with the Tc-doped systemthe introduction of VS does not lead to a significant change in the total magnetic moment of the (TcVS) co-doped systemand the magnetic moment of the doped system is mainly contributed by the Tc atom. In the 2Tc-doped systemthe most stable configuration was determined by formation energy analysis. The magnetic moment of the 2Tc-doped system is 2048 μB and mainly comes from two Tc atoms. The spin charge density analysis shows that the (Tc-4d)-(S-3p)-(Mo-4d)-(S-3p)-(Tc-4d) coupling chain may be the reason for the ferromagnetic coupling of the 2Tc-doped system.