Abstract. The w-index of a surface link F is the minimal number of the triple points of surface braids representing F . In this paper, for a given 3-cocycle, we consider the minimal number of the w-indices of surface links whose quandle cocycle invariants associated with f are non-trivial, and denote it ω(f ). In particular, we show that ω(θ 3 ) = 6 and ω(θ p ) ≥ 7, where θ n is Mochizuki's 3-cocycle of the dihedral quandle of order n and p is an odd prime integer = 3. As a consequence, for a given non-negative integer g, there are surface knots with genus g with the w-index 6.