Given a closed manifold M and a vector bundle ξ of rank n over M, by gluing two copies of the disc bundle of ξ, we can obtain a closed manifold D(ξ,M), the so-called double manifold.In this paper, we firstly prove that each sphere bundle Sr(ξ) of radius r>0 is an isoparametric hypersurface in the total space of ξ equipped with a connection metric, and for r>0 small enough, the induced metric of Sr(ξ) has positive Ricci curvature under the additional assumptions that M has a metric with positive Ricci curvature and n≥3.As an application, if M admits a metric with positive Ricci curvature and n≥2, then we construct a metric with positive Ricci curvature on D(ξ,M). Moreover, under the same metric, D(ξ,M) admits a natural isoparametric foliation.For a compact minimal isoparametric hypersurface Yn in Sn+1(1), which separates Sn+1(1) into S+n+1 and S−n+1, one can get double manifolds D(S+n+1) and D(S−n+1). Inspired by Tang, Xie and Yan's work on scalar curvature of such manifolds with isoparametric foliations (cf. [25]), we study Ricci curvature of them with isoparametric foliations in the last part.