Abstract: Kinesin spindle protein (KSP/Eg5) is essential for the formation and maintenance of bipolar spindles during mitosis. Inhibition of this protein leads to cell cycle arrest and apoptosis without interfering other microtubule-dependent processes. Therefore, it is a potential target in cancer therapy. Here, a series of tetrahydro-β-carboline derivatives 5a-k were synthesized as kinesin spindle protein inhibitor. Their structures were confirmed with ¹H NMR, ESI-MS and elemental analysis. The synthesized compounds were evaluated for their inhibition of KSP.