The burgeoning field of sustainable tourism in historically significant urban districts has derived increasing attention in tandem with broader urban economic development. The perceived image of a tourist destination significantly affects tourist consumption behaviors and destination choices, while negative evaluations provide destination managers with insights for targeted improvements to tourist amenities, thereby contributing to the sustainable development of these historically significant districts. This study leveraged Python 3.12.3 software to collect online textual data from popular tourism websites, specifically Ctrip 8.71.4 and Mafengwo 11.1.7. Then, ROST CM6.0 software facilitated high-frequency word analysis, network semantic analysis, and sentiment analysis to outline the perceived image and characteristics of the Macau Historic District, a UNESCO World Heritage site, from the perspective of tourists. The findings are as follows: (1) The image of the Historic Centre of Macao as a tourist destination comprises four primary dimensions: cultural (16.02%), landscape (30.85%), emotional (16.97%), and local (36.16%). (2) Tourists perceive the Historic Centre of Macao as a blend of dynamism and tranquility, tradition, and modernity. (3) Emotional evaluations of the Historic Centre of Macao as a tourist destination are primarily positive (85.45%), whereas negative sentiments constitute 5.76%, with recurring themes pertaining to overcrowding, high prices, a lack of interactive experiences at attractions, excessive commercialization, and insufficient public rest facilities. These findings offer valuable directives for the future planning and development of tourism in Macau, a city recognized for its World Heritage status. (4) In summary, the thematic image of the Historic Centre of Macao can be considered authentic, romantic, and commercialized.