A unique cobalt nanomountain array supported Si film was successfully fabricated by the combination of electrodeposition and radiofrequency magnetron sputtering. The nanostructured Si film with a proper thickness shows excellent cyclic performance with a high discharge capacity of 1917.8mAhg−1 after 100 cycles at 0.1C, also presents high rate capability with revisable capacities of 1953.3mAhg−1 at 0.5C and 1166.1mAhg−1 at 3C. The improved electrochemical performance can be attributed to the strengthening adhesion of the Si film to the cobalt nanomountain arrays and the formation of an island structure within the film, which provide good mechanical support and electron conducting pathway. The well-designed nanostructured Si electrode is a promising material for application of lithium ion batteries.