This study aims to generate a systematic approach to exploring smellscape, from understanding and interpretation to evaluation and design in a specific type of public space - urban intermodal transit spaces, that large numbers of people visit every day, and which have intensive traffic flows and various functions. Taken Grounded Theory as a methodological approach, this study took one typical case from each country, Wuchang Railway Transit Centre and Sheffield Railway Station and Bus Interchange, to explore smellscapes in intermodal transit spaces in China and UK. An analytic procedure has been generated from the studied cases explaining people’s perception of smell environments through key elements in the concept, influenced by eleven perceptual patterns. This analysis answers the question of how to understand and interpret smellscape. In terms of people’s assessment of the pleasantness of smellscape, nine indicators were identified, which have been developed into a framework for measuring smellscape quality and classifying different types of smellscapes. The most dominant type of pleasantness in urban intermodal transit spaces is mainly influenced by cleanness and freshness. The perceptual process and evaluation criteria help with understanding and analysing existing smellscapes, and also inform the design objective for achieving a pleasant smellscape in target spaces. In terms of designing a pleasant smellscape in the target context, a design framework has been constructed at three scales with design methods and examples, responding to identified components from smells and smell sources, individual differences, physical environmental settings and contextual issues. This also gives an example of integrating smellscape design into a traditional design framework for a specified functional public space at the macro, midi and micro levels.