Rovibrational bands spectra of three ν20, ν7 and ν19 bands of 1, 3, 5 – trioxane (H2CO)3 were recorded in the 50–650 cm−1 range using a long path absorption cell coupled to a high resolution Fourier transform spectrometer and synchrotron radiation at the AILES beamline of the SOLEIL synchrotron. More than 16 000 lines were assigned with a dRMS better than 0.17 × 10−3 cm−1 . Two different formalisms (tensorial and Watson) were used to derive accurate rotational and quartic parameters for the three bands and for the first time, a precise determination of Coriolis parameter and q+ l−doubling constant for both ν20 and ν19 perpendicular bands was obtained. Last, each set of spectroscopic parameters is compared and discussed between both formalisms.