The structural and magnetic properties of Y(Fe1-xMnx)12 compounds and their nitrides (x = 0.2 and 0.4) have been studied by using X-ray diffraction and magnetic measurements. It is found that the lattice parameters increase, while the saturation magnetization and Curie temperature decrease with Mn content increment in Y(Fe1-xMnx12 compounds. Y(Fe0.8Mn0.2)12 compound shows a weak easy-c axis magnetization direction, but Y(Fe0.6Mn0.4)12 compound is in a paramagnetic state at room temperature. Upon nitrogenation, the lattice parameters, Curie temperature are notably increased and the (...) saturation magnetization is greatly increased by about 50%. The easy magnetization direction for both compound nitrides all lies in the basal plane at room temperature. (shrink)