OBJECTIVE To prepare C-phycocyanin nanoparticles （CPC-NPs） and evaluate the in vitro mechanism of CPC- NPs on acute lung injury induced by lipopolysaccharide （LPS） combined with seawater. METHODS Ion crosslinking method was used to prepare CPC-NPs using CPC as the drug， carboxymethyl chitosan （CMCS） as the carrier， and CaCl2 as the crosslinking agent. The basic characterization of CPC-NPs was carried out. Mouse alveolar type Ⅱ epithelial cells MLE-12 and macrophages RAW264.7 were divided into 7 groups： normal group （Con group）， model group （Mod group）， blank NPs group， CPC-NPs 30， 60， 120 and 240 μg/mL groups. Except for the Con group， all other groups were treated with a combination of 10 μg/mL LPS and 25% seawater for 6 hours. After modeling， each treatment group was treated with corresponding drugs for 24 hours. The levels of malondialdehyde （MDA）， total antioxidant capacity （T-AOC）， superoxide dismutase （SOD）， catalase （CAT）， and glutathione peroxidase （GSH-Px） in MLE-12 cells， as well as the expression levels of B-cell lymphoma-2 （Bcl-2）， Bcl-2 associated X protein （Bax）， caspase-3 protein and mRNA， CAT and glutathione S-transferase （GST） mRNA were determined. The levels of interleukin- 1β （IL-1β）， tumor necrosis factor-α （TNF-α） and IL-6 in RAW264.7 cells， as well as the expression levels of NOD-like receptor thermal protein domain associated protein 3 （NLRP3）， cleaved caspase-1 protein， and mRNA expressions of IL-1β，TNF-α， IL-6 and inducible nitric oxide synthase （iNOS） were all detected. RESULTS The prepared CPC-NPs had particle size of （675.69±64.58） nm， Zeta potential of （－20.11± E-mail：zhangleifang1986@163.com 0.98） mV， polydispersity coefficient of 0.455±0.010 （n＝3）；entrapment efficiency of 35.60%， and drug loading of 16.13%；CPC-NPs had regular spherical shapes， where the drug could be sustainably released for more than 30 hours. Compared with Mod group， the levels of T-AOC， SOD， CAT （excluding the 30 μg/mL group of CPC-NPs） and GSH-Px， mRNA expressions of CAT and GST， as well as the Bcl-2/Bax protein ratio and mRNA ratio were significantly increased in MLE-12 cells of different concentration groups of CPC-NPs， while MDA levels and caspase-3 protein and mRNA expression were significantly reduced （P＜0.01 or P＜0.05）. Compared with Mod group， the levels of IL-1β， TNF-α and IL-6， NLRP3 and cleaved-caspase-1 protein expressions， as well as the mRNA expressions of IL-1β， TNF-α， IL-6 and iNOS in RAW264.7 cells of different concentration groups of CPC-NPs were significantly reduced （P＜0.01 or P＜0.05）. CONCLUSIONS CPC-NPs with lung targeting and sustained release property were prepared successfully， which can alleviate acute lung injury induced by LPS combined with seawater through antioxidant stress， inhibiting cell apoptosis and inflammatory response.