Let \(\mathcal {C}=(\mathcal {C},\mathbb {E},\mathfrak {s})\) be an extriangulated category with a proper class \(\xi \) of \({{\mathbb {E}}}\) -triangles. In this paper, we introduce and study quasi-resolving subcategories in \(\mathcal {C}\) . More precisely, we first introduce the notion of \(\mathcal {X}\) -resolution dimensions for a quasi-resolving subcategory \(\mathcal {X}\) of \(\mathcal {C}\) and then give some equivalent characterizations of objects which have finite \(\mathcal {X}\) -resolution dimensions. As an application, we introduce Gorenstein quasi-resolving subcategories, denoted by \(\mathcal {GQP_X}(\xi )\) , in terms of a quasi-resolving subcategory \(\mathcal {X}\) , and prove that \(\mathcal {GQP_X}(\xi )\) is also a quasi-resolving subcategory of \(\mathcal {C}\) . Moreover, some classical known results are generalized in \(\mathcal {GQP_X}(\xi )\) .