Influences of amorphous film formation on the growth of nanocrystalline Ag during replacement reactions were investigated. Amorphous films with a thickness of 5-10 nm were observed by HRTEM on the growth tip of Ag nanopaticles. The growth of Ag nanocrytallines depends on the in situ crystallization of amorphous films. Both in situ nucleation of crystalline Ag in amorphous films and without nucleation can take place. The stability of amorphous films depends on the concentration of AgNO3 solution. In 80 mmol·L-1 or lower AgNO3 solution, amorphous films can exist stably, while in 400 mmol·L-1 AgNO3 solution no amorphous films can be detected