Sepal is an important part of flower and fruit in tomato, which affect the commodity quality of fruit. Based on 40 tomato accessions of different types, we investigate the developmental process of sepal, indexes which can describe sepal morphology and diversity of sepal morphology. The results show, morphology of tomato sepals, which are called persistent calyx, changes during development of flower and fruit. The sepal development process was subdivided into 7 stages: close, slightly open, fully open, close again, open again, morphological change, final morphology. The final morphology divided into five types : flat spread, upwarp, upright, up-curl and down-wrap. The coefficient of variation of 7 sepal traits are crimpness (SEC, 84.43%), surface area (SESA, 45.54%), upwarp degree(SEUD, 40.93%), shape coefficient (SESC, 36.05%), length (SEL, 35.02%), thickness (SET, 29.46%) and width (SEW, 24.61%) from high to low. Correlation analysis reveals, significantly positive correlation is found among the SEL, SEW, SET and SESA; significantly positive correlation is showed between SESC(SEL/SEW) and SEL, but not between SESC and SEW; the correlation between SEC and SEUD is significantly positive, but there are not significant correlations between these 2 traits and other 5 traits. The PCA shows that the first 3 PCs can represent the 7 traits, the cumulative contribution rate of PC1 (size traits), PC2 (shape traits) and PC3 (morphology traits) add up to 87.5%. 5 types of sepal morphology are described with the morphological indexes.