In this article, conjugate-linear anti-involutions and -unitary HarishChandra modules over the W-algebra W(2,2) are studied. It is proved that there are only two classes that conjugate-linear anti-involutions over W(2,2). The main result of this article is that a -unitary Harish-Chandra module over the W-algebra W(2,2) is simply a -unitary Harish-Chandra module over the Virasoro algebra and hence is either a simple highest or lowest weight module or a simple module from the intermediate series of the form A a,b for some a 2 R, b 2 1 2 þ ffiffiffiffiffiffi ffi À1 p R: