Five new cassane-type diterpenoids, including 16-O-ethyl caesalpin A (1), 16-O-ethyl caesalpin B (2), norcaesalpinin ME (3), 6α-hydroxynorcaesalpinin A (4), and 17-acetylcaesalmin Z (5), were isolated from the seeds of Caesalpinia minax Hance, along with twelve known compounds. The structures of the new compounds were established by means of spectroscopic technique (NMR, HRESIMS and IR). The absolute configurations of the new compounds were determined by their ECD spectra. In palmitic acid/oleic acid-treated AML12 mouse hepatocytes, compound 5 greatly reduced intracellular lipid accumulation, as well as total triglyceride and cholesterol contents, which could be further developed to treat fatty liver disease.