Objective To investigate the value of plasma long non-coding RNA MALAT1 in the diagnosis, severity and prognosis of sepsis. Methods Totally 60 sepsis patients admitted to the ICU of the First People""s Hospital of Yancheng, between January 2017 and January 2018, were recruited into this prospective study. Meanwhile, 30 healthy controls were also recruited. The clinical data of all subjects were collected, and the expression level of plasma MALAT1 was detected by reverse transcription-polymerase chain reaction (RT-PCR). The receiver operating characteristic curve (ROC) was used to analyze the predictive value of MALAT1 for the diagnosis, severity and prognosis of sepsis. Results The expression level of plasma MALAT1 was gradually increased among healthy control, sepsis and septic shock groups (all P<0.05). The expression level of plasma MALAT1 in the death group was significantly higher than that in the survival group (P<0.05). The area under the ROC curve (AUC) for MALAT1 to predictive sepsis diagnosis was greater than that for serum procalcitonin (PCT) level (0.963 vs 0.898). The AUC for MALAT1 to distinguish septic shock from sepsis is less than those for the lactate level, sequential organ failure score (SOFA) and acute physiology and chronic health evaluation II (APACHE II) score (0.784 vs 0.880, 0.849 and 0.831). The AUC for MALAT1 to predictive sepsis prognosis is less than those for the lactate, SOFA, and APACHE II score (0.876 vs 0.923, 0.952 and 0.907). Conclusion The expression level of plasma MALAT 1 has a good predictive value for the diagnosis and prognosis of sepsis, and can be used as a diagnostic and prognostic biomarker of sepsis.