Blood sera of 12 severe Covid-19 patients and 14 healthy human donors were subjected to original TCA-extraction/acetone-precipitation followed by SDS-PAAG electrophoresis and mass-spectrometry. 76 kDa protein was detected as one of the differentially expressed proteins in the samples of Covid-19 patients. This 76 kDa protein was identified with mass-spectrometry as human serum albumin. Such molecular form of albumin was absent in blood serum of healthy human donors. The potential ways of generation of the unusual form of human serum albumin and its probable diagnostic value were discussed. Keywords: acetone-precipitation, biomarker proteins, COVID-19, electrophoresis, mass-spectrometry, TCA-extraction, unusual form of human serum albumin