This paper considers the asymptotic behavior for the tail probability of randomly weighted sum Sθ 2 = θ1X1+θ2X2, where X1, X2, θ1, and θ2 are non-negative dependent random variables with distributions F1, F2, G1, and G2, respectively. We obtain the tail-equivalence of P Sθ 2 > x and P(θ1X1 > x)+P(θ2X2 > x) as x → ∞ and some closure properties of distribution classes in three cases: (i). θ1, θ2 are bounded and F1, F2 are subexponential; (ii). θ1, θ2 satisfy the condition of Theorem 2.1 of Tang (2006) [33] and F1, F2 are subexponential with positive lower Matuszewska indices; (iii). θ1, θ2 satisfy the condition of Theorem 3.3 (iii) of Cline and Samorodnitsky (1994) [12] and F1, F2 are long-tailed and dominatedlyvarying- tailed. Furthermore, when F1 and F2 are regularly-varying-tailed, a more transparent result is established and applied to obtain asymptotic results for risk measures. Some numerical studies are conducted to check the accuracy of the obtained results.