In this research, microstructural evolution and magnetic behavior of (Co70Fe30)70Zr10Nb5B15 alloy prepared by mechanical alloying were investigated and the effect of milling time on structural and magnetic properties of this alloy was investigated. The structural properties have been investigated by X-ray diffraction )XRD), scanning electron microscopy (SEM), High resolution transmission electron microscope (HRTEM), energy dispersive X-ray spectroscopy (EDX). The magnetic properties were also investigated by vibrating sample magnetometer (VSM). Furthermore, the heat treatments of the samples were investigated by using differential scanning calorimetry (DTA). X-ray diffraction showed the structural and morphological evolution of the alloy with increasing milling time, so that the images taken after 180 hours of crystallite size indicated the flatness and regularity of the final composition. After 180 hours of milling, the crystallite size of the sample reached its lowest value, i.e. 23 nm. The lattice strain during the milling period of the sample had the reverse trend of the crystallite size, and the highest strain occurred at 180 hours, which it’s value was equal to 0.31%. Based on the results obtained for the saturation magnetization and the coercivity, it was determined that the lowest value of saturation magnetization occurs after 10 hours of milling and the highest value occurs after 40 hours. Also, the lowest value of the corecivity was created after 40 hours and the highest value after 180 hours of milling. The heat treatment at and and milled for 180 hours showed the crystalline constituent elements Fe, Co, ZrO2, Co7Fe3. Also, the heat treatment for the 180 hours sample leaded to increase of crystallite size and saturation magnetization and decrease in coercivity. The findings indicated soft ferromagnetic behavior, particularly for the annealed samples.