Nanostructured Ag with different morphologies and structures was prepared by replacement reaction (Zn versus AgNO3). The influence of AgNO3 concentration on the growth speed, the morphology and the structure of the nanostructured Ag was investigated. Experimental results show that the growth speed, morphologies and structures of the nanostructured Ag strongly depend on AgNO3 concentration and reaction time. The growth speed is mainly dependent on the AgNO3 concentration; the higher the concentration, the faster the growth speed. When the AgNO3 concentration is 5 mmol/L, Ag fractal forms at the beginning stage, but the fractal transforms to dendrite consisting of nanoparticles and to monocrystal at last as the reaction proceeds. When the concentration is in the range of 20-100 mmol/L, the products are all Ag dendrites, but the dendrites consist of nanoparticles when the concentration is below 40 mmol/L while they are monocrystal when the concentration is above 60 mmol/L. Ag nanostructures with different morphologies and structures can be prepared by controlling AgNO3 concentration and reaction time.