Electromagnetically induced transparency (EIT) resonance is obtained in a Λ three-level configuration when the coupling field and the probe field satisfy the two-photon resonance condition. When an additional microwave field drives the transition between two low levels of the Λ three-level system the EIT is observed to split into multiple EITs. In this paper we present a theoretical study of this effect. The results show that the EIT resonance can be split into triplet and the spectral positions of EIT windows is determined by the intensity and the frequency of the microwave field. Therefore, a microwave field can be used to open more than one EIT windows and the EIT frequency tuning can be realized by controlling intensity and frequency of the microwave field.