At CRYPTO 1991, Koblitz proposed the anomalous binary curves for speeding up scalar multiplication in elliptic curve cryptosystem. At CRYPTO 1997, Solinas proposed the \tau-NAF method on Koblitz curves and reduced the Hamming weight of the scalar to n/3 over the field F_2n. AtPKC 2004, Avanzi et al combined the \tau-NAF with one point halving and reduced the Hamming weight of the scalar to 2n/7. Recently, Avanzi et al improved this method by introducing the wide-double-NAF whose Hamming weight is n/4. In this paper, we propose the wide-w-NAF, which is an extension of Avanzi's wide-double-NAF, and reduce the Hamming weight to n/(w+1). When n \ge 144, our method is at least 43% -- 56% faster than Solinas's \tau-NAF method and 21% -- 39% faster than Avanzi's wide-double-NAF method without additional memory requirements.