This paper presents a long length discrete Hartley transform (DHT) design with a new hardware efficient distributed arithmetic (DA) approach. The new DA design approach not only explores the constant property of coefficients as the conventional DA, but also exploits its cyclic property. To efficiently apply this approach to long length DHT, we first decompose the long length DHT algorithm to short ones using the prime factor algorithm (PFA), and further reformulate it by using Agarwal-Cooley algorithm such that all the partitioned short DHT still consists of the cyclic property. Besides, we also exploit the scheme of computation sharing on the content of ROM to reduce the hardware cost with the trade-off in slowing down the computing speeds. Comparing with the existing designs shows that the proposed design can reduce the area-delay product from 52% to 91% according to a 0.35 µm CMOS cell library.