The isothermal section of the Mn-Zr-Si ternary system at 600℃ was investigated by using X-ray diffraction, scanning electron microscope and energy dispersive analysis. A new termary compound was discovered. This compound was found to be isostrutural to Fe4Si7Zr4 with tetralgonal structure and cell parameters of a = 1.3027 nm, c = 0.515 nm. A quite different conclusion was obstained for the Zr-Si binary system comparing to results in the literatures. No the evidence was found to support the existence of Zr3Si at 600℃, which was taken as a stable phase in the Zr-Si system. Moreover, XRD and SEM/EDS revealed that Zr5Si3 was a stable phase at 600℃. In addition, MnSi2Zr and MnSiZr were confirmed at 600℃ while Mn4Si6Zr3 is not found in the present work.