In order to further investigate the micro-nano scale monocrystalline germanium cutting mechanism, the molecular dynamics method was firstly used to simulate the stress field distribution of material atoms and the influence of different tool angles on stress distribution. The average stress value of hydrostatic and Von Mises at various times during the cutting process are calculated by nearest neighbor average method. The results show that during the nano-cutting process of monocrystalline germanium, the maximum average stress value is concentrated in the subsurface region of the tool tip, and the maximum stess is 8.6Gpa. There is also a high stress in the chip, which is around 4.2Gpa. In addition, the angle of the tool also has an influence on the distribution of the stress field. The cutting force curves of different tool angles are drawn. It is found that the tool rake angle has a significant influence on the cutting force. The cutting force is the largest when cutting with a negative rake angle, while the relief angle has no effect on the cutting force, which is consistent with the macro cutting theory.