Δ-moves are closely related with a Vassiliev invariant of degree 2. For classical knots, M. Okada showed that the second coefficients of the Conway polynomials of two knots differ by 1 if the two knots are related by a single Δ-move. The first author extended the Okada’s result for virtual knots by using a Vassiliev invariant of virtual knots of type 2 which is induced from the Kauffman polynomial of a virtual knot. The arrow polynomial is a generalization of the Kauffman polynomial. We will generalize this result by using Vassiliev invariants of type 2 induced from the arrow polynomial of a virtual knot and give a lower bound for the number of Δ-moves transforming K₁ to K₂ if two virtual knots K₁ and K₂ are related by a finite sequence of Δ-moves.

Keywords: Δ,-move, arrow polynomial, Miyazawa polynomial, virtual knot, Vassiliev invariant