Objective to investigate the application value of PiCCO monitoring in the diagnosis and treatment of critically ill patients, and to analyze its application prospects. Methods 200 cases of critically ill patients, after admission to the PAC and PiCCO, starting test after three time of 1min, 12h, 1D detection data observation data including heart rate (HR), mean arterial pressure (map), cardiac output (CO), central venous pressure (CVP), thoracic cavity blood volume index (ITBVI), extravascular lung water index (EVLWI), and carries on the contrast analysis. Results the six indexes of the patients were found by sphere test, P>0.05, in accordance with the spherical distribution, and the follow-up results were analyzed by repeated measures analysis of variance. The results showed that there were significant differences in the six indicators (P<0.05) at different time points, but there was no difference between the group and the time of the group (P>0.05). Six indicators of patients with two indicators of different time points, there are significant differences, but the two time points of comparison, there is no difference. Conclusion the two kinds of detection of similar income hemodynamics, but PiCCO can further measurements ITBVI and EVLWI and impact to judge the liquid and blood capacity and larger for critically ill patients with great application value, with the prospect of further promotion and research.