Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling of the precapillary pulmonary arteries, with excessive proliferation of vascular cells. This study was performed to examine the effects of long noncoding RNA CPS1 intronic transcript 1 (CPS1-IT) on PAH in rat models of obstructive sleep apnea (OSA) through regulating interleukin (IL)-1 beta expression. The OSA models were induced in rats, for determination of the CPS1-IT expression. The binding of CPS1-IT and hypoxia-inducible factor 1 (HIF1) was verified. To analyze the effects of CPS1-IT on PAH, the overexpression vector of CPS1-IT and HIF1, shRNA against IL-1 beta and pyrrolidine dithiocarbamate (PDTC, inhibitor of the NF-kappa B signaling pathway) were injected into rat models, respectively. The blood pressure and activity of biochemical indicators including nitric oxide (NO), nitric oxide synthase (NOS), superoxide dismutase (SOD), and lipid peroxide (LPO) were assessed. The expression of IL-1 beta, HIF1, alpha-smooth muscle actin (alpha-SMA), proliferating cell nuclear antigen (PCNA), and fibronectin (FN) was determined. The relationship of CPS1-IT to IL-1 beta and NF-kappa B was evaluated. CPS1-IT was downregulated in the OSA rat model. Overexpressed CPS1-IT increased the activity of NO, NOS, and SOD as well as alpha-SMA expression, whereas decreasing LPO activity and expression of PCNA and FN, whereby PAH was suppressed. Notably, overexpressed CPS1-IT reduced IL-1 beta expression through NF-kappa B signaling pathway via inhibiting the HIF1 transcriptional activity, suggesting a mechanism affecting PAH. To conclude, overexpressed CPS1-IT alleviated PAH in OSA by reducing IL-1 beta expression, the mechanism of which was involved with inhibited HIF1 transcriptional activity and the NF-kappa B signaling pathway.