Forty-three quinolizidine alkaloids (1–43), including twelve new matrine-type ones, sophalodes A–L (1–7, 17, 19 and 28–30), were isolated from the seeds of Sophora alopecuroides. Structurally, compounds 1–4 were the first examples of C-11 oxidized matrine-type alkaloids from Sophora plants. The structures and absolute configurations of new compounds were elucidated by extensive spectroscopic techniques, X-ray diffraction analysis, and quantum chemical calculation. In addition, the NMR data and absolute configuration of compound 18 was reported for the first time. All the isolates were evaluated for their inhibition on nitric oxide production induced by lipopolysaccharide in RAW 264.7 macrophages, among them, compounds 29, 38 and 42 exhibited the most significant activity with IC₅₀ values of 29.19, 25.86 and 33.30 μM, respectively. Further research about new compound 29 showed that it also suppressed the protein levels of iNOS and COX-2, which revealed its anti-inflammatory potential. Moreover, additional research showed that compound 16 exhibited marginal cytotoxicity against HeLa cell lines, with an IC₅₀ value of 24.27 μM.