Abstract: A novel protein named malanin was purified from the seeds of Malania oleifera, and its inhibitory effect was determined on the growth of human leukemia K562 cells in vitro. The result showed that malanin could significantly inhibit the viability of K562 cells in a time and dose-dependently manner, producing the half inhibitory concentration IC50 value of 1.58×10-8mol·L-1. Malanin combined with cisplatin showed a significant synergistic inhibitory effect, and the effect of two drugs combined treatment would increase. In addition, malanin had good thermal stability and very easy storage. It provided a basis and ideas for malanin on development and utilization in cancer therapy, and it was also to lay the foundation for the protein as the research and development of new drugs.