We present the theory of a new type of topological quantum order which is driven by the spin-orbit density wave order parameter, and distinguished by a Z(2) topological invariant. We show that when two oppositely polarized chiral bands [resulting from the Rashba-type spin-orbit coupling ak; k is crystal momentum] are significantly nested by a special wave vector Q similar to (pi, 0)/(0, pi), it induces a spatially modulated inversion of the chirality (alpha(k+ Q) = alpha*(k)) between different sublattices. The resulting quantum order parameters break translational symmetry, but preserve time-reversal symmetry. It is inherently associated with a Z2-topological invariant along each density wave propagation direction. Hence it gives a weak topological insulator in two dimensions, with even number of spin-polarized boundary states. This phase is analogous to the quantum spin Hall state, except here the time-reversal polarization is spatially modulated, and thus it is dubbed quantum spin Hall density wave (QSHDW) state. This order parameter can be realized or engineered in quantum wires, or quasi-two-dimensional systems, by tuning the spin-orbit coupling strength and chemical potential to achieve the special nesting condition.