This paper proposes parallel implementation of the prime-factor discrete Hartley transform algorithm on the orthogonal-multiprocessor (OMP) architecture when the transform size N is decomposable into two mutually prime numbers N = N 1 N 2. The implementation shows that the existing prime-factor DHT algorithm can be mapped easily on the architecture without modification. The proposed algorithms include input index mapping, summation, scaling, matrix transpose, adjust-add and output index mapping. The resulting algorithm can be accomplished in N 1 + N 2 multiplication steps on a J processors OMP, where J is the maximum dimension of scaling matrices ( C ̂ N 1 , C ̂ N 2 ).