To explore the resistance function of chitinase to gray mold disease in Lilium spp. A chitinase gene (named as LoChi2) was cloned by reverse transcription PCR from Botrytis elliptica-infected leaves of L. oriental hybrid ‘Sorbonne’. The open reading frame of LoChi2 is 915 bp long and encodes 304 amino acids with a predicted molecular weight of 32.52 kD and a calculated isoelectric point of 4.16. Protein structural and phylogenetic analyses revealed that LoChi2 is a member of Class Ⅲ from glycoside hydrolase 18 family. As a secretory protein with hydrophobicity, LoChi2 is located outside the cell. It includes a conserved GH18 narbonin catalytic domain, a transmembrane domain, as well as signal peptide, glycosylation, and phosphorylation sites. Multiple sequence alignment of the deduced amino acid sequence of LoChi2 displayed high similarity with the sequences of several Chi2 genes from L. longiflorum, Ananas comosus, and Prunus mume. qRT-PCR analysis showed that the expression levels of LoChi2 were positively correlated with gray mold disease resistance among different cultivars. More transcripts of LoChi2 accumulated in the highly resistant cultivar ‘Sorbonne’ than in the moderately susceptible L. × formolongi ‘Raizan 3’ and highly susceptible L. asiatic hybrid ‘Tresor’ after infected with B. elliptica. Furthermore, the expression of LoChi2 was induced by exogenous salicylic acid and jasmonic acid treatments. This study lays a foundation for further research on the biological function of LoChi2 gene, and provides potential gene source for the molecular breeding of Lilium with enhanced Botrytis-resistance.