The work is devoted to the experimental study of the regularities of laminar-turbulent transition in supersonic boundary layers. The experiments were carried out in the low-noise supersonic wind tunnel T-325 of ITAM SB RAS. The measurements were made by a constant-temperature hot-wire anemometer in the scanning mode. The procedure of decomposition of the fluctuations of the boundary layer into temperature and mass flux disturbances was carried out. The level of pulsations in the free flow of the test section of the T-325 wind tunnel was determined. The laminar-turbulent transition of two-dimensional supersonic boundary layer was experimentally investigated at Mach number M = 2 and 2.5. The levels of total temperature and mass flow pulsations were measured. It was found that at the laminar-turbulent transition process the ratio of the mass flow and total temperature pulsations remains almost constant.