A varied and constant load nano-scratch experiment on monocrystalline germanium was performed by Cube indenter. The surface morphology of the groove was observed by scanning electron microscope (SEM) and atomic force microscope (AFM) , and the scratch process was divided into three regimes, that is ductile regime, ductile-brittle transition regime and brittle regime based on observations. The material removal mechanism of different regimes was also analyzed. The least square method was used to establish nonlinear curve fittings between scratch depth and scratch force, and the correlation coefficient was used to verify reliability of fitting functions. Result shows that there is a strong correlation between scratch depth and scratch force. Meanwhile, the tendency of elastic recovery rate with scratch distance was analyzed. As the result shows, the elastic recovery rate gradually decreases from 1 in the pure elastic stage to about 0.76 in stable stage. Based on ductile-brittle translation critical load, a model is proposed to calculate the critical depth where the elastic recovery rate is firstly considered, and the ductile-brittle translation critical depth for monocrystalline germanium is 489 nm.