Frozen sand mold is a green casting process with molding sand and water-based binder as molding material. Digital milling forming technology based on the principle of material reduction can realize high-precision and efficient processing of frozen sand molds. The frozen sand mold prepared by 70/140 mesh dried silica sand mixed with 5%(mass fraction) water was taken as the research object. In the forming temperature range of -25 to -20 ℃, the influence of milling parameters on the milling force of the frozen sand mold was investigated by digital precision forming machine without pattern casting. The milling force signal measured by the 9253B cutting force meter was processed and analysed by fast Fourier transform(FFT). The influence mechanism of each milling forming parameter on the milling force of the frozen sand mold was revealed by the control variable method. The results show that the milling force signal is composed of a single signal. The period of the milling force signal is proportional to the period of the spindle speed. The amplitude of the milling force signal increases with increasing feed rate, milling width and milling depth.