Six new (<b>1</b>-<b>6</b>) and two known (<b>7</b>, <b>8</b>) alkaloids that were chemically inseparable geometrical isomers (two isomers present in a 1:1 ratio for <b>1</b>-<b>4</b> and <b>6</b> and a 1:3 ratio for <b>5</b>, <b>7</b>, and <b>8</b>) were identified from <i>Stephania cepharantha</i>. Their structures and absolute configurations were determined by spectroscopic data analyses and comparison of their experimental and calculated ECD spectra. Moreover, using NOE correlations and DFT-based calculations, the NMR data of each geometrical isomer of <b>1</b>-<b>6</b> were assigned. The biological evaluation of <b>1</b>-<b>8</b> showed that <b>5</b> and <b>6</b> have stronger inhibitory effects (IC<sub>50</sub> values, 12.0 and 12.6 μM, respectively) than minocycline (IC<sub>50</sub> value, 17.5 μM) against NO production in overactivated BV2 cells, suggesting they have great potential in the development of neuroinflammatory therapeutics for treating neurodegenerative diseases.