A new pathogen Nosema glabripennis Zhang parasiting the longhorned beetle Anoplophora glabripennis. According to the field investigation, about 2.8% of the real pathogens for naturally dead longhorned beetles were microsporidiums and the other pathogens were mostly saprophytic or other parasitic organisms, which parasitized the beetles after infection by the microsporidium. The results of bioassey showed that the mortality of the longhorned beetle larvae was 27.4%. The microsporidium possesses the ability of vertical dissemination and was hopeful to be an effective natural organism to control the beetles.