YTi(Fe1-xCox)11 crystallizes in the ThMn12-type tetragonal structure, with x ranging from 0.0 to 1.0, the Curie temperature increases with the increase of Co content. In order to understand the relation between magnetic properties and microst-ructure of these compounds, we studied their M?ssbauer spectra. The M?ssbauer effect measurements were carried out at room temperature on YTi(Fe1-xCox)11, with x equal to 0.0, 0.2 and 0.4. The best fits confirm that Co atoms preferentially occupy the j and f sites. The hyperfine fields of the measured samples reach a maximum at x = 0.2,which is in agreement with the results of magnetic measurements. By comparing the experimental results of M?ssbauer spectra of YTi(Fe1-xCox)11, Y2(Fe1-xCox)14B and YTi(Fe1-xNix)11, we analyze the difference of the 3d band structure between YTiFe11, and Y2Fe14B.