In this paper, we introduce a definition of λ-hypersurfaces of weighted volume-preserving mean curvature flow in Euclidean space. We prove that λhypersurfaces are critical points of the weighted area functional for the weighted volume-preserving variations. Furthermore, we classify complete λ-hypersurfaces with polynomial area growth and H−λ ≥ 0, which are generalizations of the results due to Huisken [19], . We also define a F -functional and study F -stability of λ-hypersurfaces, which extend a result of Colding-Minicozzi [11]. Lower bound growth and upper bound growth of the area for complete and non-compact λ-hypersurfaces are also studied.2001 Mathematics Subject Classification: 53C44, 53C42. Key words and phrases: the weighted volume-preserving mean curvature flow, the weighted area functional, F -stability, weak stability, λ-hypersurfaces.