The nanoscale crack propagation behavior in the presence of nonlinear disturbance strains is studied by using the phase‐field‐crystal method. The influences of amplitude A and frequency ω on fracture mode and crack growth are discussed. The simulation results suggest that the disturbance strains can make fracture mode change between brittle fracture and ductile fracture. When amplitude A is large, increasing frequency ω will lead to the brittle‐to‐ductile transition (BDT). Further increasing ω can make ductile‐to‐brittle transition (DBT) happen. Meanwhile, the value of A can influence the critical frequencies for BDT and DBT. Crack growth is also affected by the disturbance strains. When ω is small, increasing ω or A can accelerate crack growth. When ω is large enough, increasing A will retard it. Through this work, we provide a new way to effectively explore the nanoscale mechanism and behavior of crack propagation.