To study the structural characteristics and seismic performance of cultural heritage buildings in Kathmandu Valley, an extensive investigation was carried out after Ms8.1 Gorkha earthquake. Brick-timber structures and masonry structures are the two major structural types in Kathmandu, Patan and Bhaktapur Durbar Squares. The structural compositions and characteristics of brick-timber structures and masonry structures were described, and analysis was done for the typical seismic damage such as wall destruction, wooden components destruction, tilt and collapse, and, reasons were studied. The seismic damage degree of cultural heritage buildings was defined, the classification and statistics of damage to the cultural heritage buildings were carried out, and different proportions of damage levels of the two structure types were obtained. The results show that in the total 52 brick-timber structures and 16 masonry structures, the proportion of basically intact or slightly damaged of brick-timber structures is merely 28.8%, and yet the masonry structure is 18.8%, others belong to partially damaged, heavily damaged and collapse, and the seismic performance of brick-timber structures are better than masonry structures. Based on the results of the seismic damage investigations, and compared with the protective principle of cultural heritage buildings, some recommendations on the reinforcement measures of cultural heritage buildings were put forward.