In this article, orientation relationships (ORs) at martensite/austenite interface (M/A interface) transformed from coarse-grained and ultrafine-grained austenites were investigated. The results showed that the OR at the M/A interfaces of lenticular martensite transformed from coarse-grained austenite was close to Kurdjumov-Sachs (K-S). The OR of butterfly martensite was close to K-S in the outer side of M/A interface and it deviated to Nishiyama-Wasserman (N-W) at the inner side of M/A interface. In contrast, the OR of lenticular martensite transformed from ultrafine-grained austenite was close to Greninger-Troiano (G-T), and the OR of butterfly martensite was close to K-S at outer side of M/A interface and it deviated to G-T at the inner side of M/A interface. The significantly small size of martensite plate transformed from ultrafine-grained austenite resulted in the different ORs from coarse-grained austenite.