Objective To study the chemical composition of and identify its active components.Methods The chemical constituents of Dendrobium Primulinum were extracted using solvents,followed by separation through silica gel and gel column chromatography,with structural identification performed via spectral analysis.The in vitro activity screening of some compounds was conducted using the MTT assay.Results Seven compounds were isolated and identified from Dendrobium primulinum,namely 7-dihydroxy-2,4-methoxyphenanthrene(1),densiflorol B(2),3,4,7-trihydroxy-2-methoxy-9,10-dihydrophenanthrene(3),thunalbene(4),phillygenin(5),3 β-hydroxy-5 α,8 α-epidioxyergosta-6,22-diene(6)、4-hydroxy-3,5-dimethoxy--cinnamaldehyde(7).Antitumor activity tests were performed on compounds 1 to 5,revealing that compound 1 exhibited strong inhibitory activity against the MCF-7/S cell line,with an IC50 of 5.13 μM.Conclusion Compounds 1 to 6 are reported for the first time from Dendrobium primulinum,while compound 7 is reported for the first time from this genus.