The 2015 Nepal earthquake caused immeasurable damage to the world cultural heritage sites in Kathmandu Valley. In order to explore the overall distribution and characteristics of this damage, a field investigation was carried out on the seismic damage to the world cultural heritage buildings in the valley, including establishment of three categories of damage. Seismic damage maps of six world cultural heritage sites were created and then analyzed statistically. In the three Durbar (royal palace) Squares of Kathmandu, Patan and Bhaktapur, 39.5%, 53.3% and 50.0%, respectively, of the cultural heritage buildings were basically well-preserved. The main bodies of Swayambhunath, the Great Boudha Stupa and Changu Narayan Temple were basically well-preserved, but the affiliated buildings were damaged to varying degrees. The soft sediments present in Kathmandu, Patan and Bhaktapur Durbar Squares amplified the earthquake effect, causing serious damage to buildings. The seismic damage in Swayambhunath and Changu Narayan Temple was mainly influenced by topographic features. These research results provide reference for seismic protection of similar heritage buildings in China.