Recently, we firstly identified cognitive impairment in patients with pulmonary hypertension (PH), which was associated with the occurrence and outcomes of PH. However, the underlying mechanism remains uncertain. The functions and histopathologis of monocrotaline-induced PH (MCT-PH) rat brains were examined by behavior tests (Morris Water Maze (MWM), Y maze (YM), open field test (OFT)) and molecularbiological investiagitons, respectively. PH rats had more platform crossover numbers in MWM, fewer alternation numbers in YM, and more central zone entries in OFT than controls (all P<0.001, Figure 1). There were moderate to severe correlations between the animal performances and right ventricular systolic pressure and Fulton index (all P<0.05). The levels of vascular marker CD31 and that of pro-inflammatory factors were significantly down- and up-regulated, and hyperactivation of Iba1⁺ microglia in PH rat cortex (Figure 2). The study confirmed PH rat brains had cerebral small vessel atrophy and neuroinflammation, which may be potential mechanism for PH-induced cognitive impairment.