The utility model discloses a fixing tool for electric network installation, especially relating to an anti-slip wire tightener. The wire tightener comprises a metal clip (1), wherein the wire clip (1) is fixed with a lead (3) via a locked piece (2) positioned in a side surface of the metal clip (1), and a parallel groove clamp (4) is arranged in an interlocking position of the metal clip (1). The lead penetrating through the tightener is locked with the metal clip via the locking piece, and the parallel groove clamp in the interlocking position is firmly connected with a connection object, thereby effectively preventing off-position of the lead caused by that the wire tightener is influenced, and avoiding accidents caused by instable connection and lead skip.