Most of the existing historic buildings are masonry buildings in China. Among them, some of buildings have served for a long time, their mechanical performance deteriorated significantly. They need to be inspected thoroughly and assessed accurately for the purpose of protection. However, there is still no available engineering software designed for the reliability assessment of existing historic masonry structures. Therefore, a Masonry Assessment software Package with three modules of pre-processing, core analyzing, and post-processing was developed based on the characteristics of historic masonry building structures. In this paper, the development technology for the software is introduced, and the suitability of the software is verified through the application of the software in a real historic masonry building.