ABSTRACT
Rare diseases are usually defined as diseases with a low incidence in the population. According to re-ports, there were 6084 rare diseases found worldwide in 2016, involving 3715 related genes. 80% of rare diseases are caused by heredity, dominant or recessive inheritance or mutations. The definition of rare diseases by”incidence”in the population varies from country to country, like the EU <1/2000 and the United States <1/2500. A drug used to prevent, treat, or diagnose a rare disease is called an orphan drug. Due to the difficulty of research and development in this small target population, the high investment risk and the high R&D cost, the problem associated with high price of orphan drugs is very prominent. In the cost-effectiveness evaluation, the resulting incremental cost-effectiveness ratio(ICER)is likely to exceed the willingness to pay threshold adopted by most countries and regions, resulting in multiple countries raising its willingness to pay threshold reference standard(3-25 times GDP per capital)for orphan drugs, or simply ex-empting health technology assessment(HTA)assessment for orphan drugs and only evaluating the impact on medical in-surance fund. This paper systematically reviewed the various internationally accepted orphan drug HTA assessment meth-odologies. Based on the characteristics of rare diseases, the paper discusses the establishment of a model for the evalua-tion of orphan drugs and the multi-dimensional value assessment framework for HTA. At the same time, according to the internationally accepted norm, the paper also explores the way to determine the willingness to pay threshold in HTA as-sessment for orphan drugs in China.