This paper presents a novel implementation of rank-order filtering using maskable memory. Based on a generic bit-sliced rank-order filtering algorithm the proposed design uses a special-defined memory, called parallel maskable memory (PMM) to realize major operations of rank-order filtering, threshold decomposition and polarization. In conventional designs, these operations are usually implemented as logic circuit and require complex computation. Using the memory-oriented architecture, the proposed rank-order filter can benefit from high flexibility, low cost and high speed. PMM has features of bit-sliced read, partial write, and pipelined processing. Bit-sliced read and partial write are driven by maskable registers. The maskable registers allows PMM to configure operating bits for parallel read/write operations. Combining the bit-sliced read with polarization selector allows PMM to perform polar determination while the partial write achieves polarization. Recursively combining the bit-sliced read and partial write, PMM can effectively realizes rank-order filtering in terms of cost and speed.