Ontology which is a description of knowledge has been applied to many fields. Some intelligent systems based on ontology have been developed. In the paper, a clothing recommendation system based on ontology is developed. The recommendation system mainly includes two parts: knowledge base and inference engine. The structural knowledge of clothing is represented by using ontology and some constraint knowledge is described by SWRL. The clothing recommendation process are carried out using JESS, a rule engine for the Java platform, by mapping OWL-based clothing knowledge and SWRL-based design rules into JESS facts and JESS rules, respectively.