This invention relates to geology, geochemistry, oil refinery and petroleum chemistry and can be implemented for determination of paraffin and asphaltene concentration in oil, in particular, for analysis of heavy oils and bitumens. To determine concentration of paraffins and asphaltenes in oil, three crude oil samples are extracted; two extracted samples are dissolved in a solvent and the solvent alongside with light oil fractions is then removed; meanwhile, asphaltenes are removed from one of the solvent-treated samples. A nucleic magnetic resonance method is employed for measuring free inductance drop-down curves for all three samples; thereafter, a ratio of solid hydrogen-containing fractions suspended in oil, to liquid hydrogen-containing fractions is defined. The paraffin concentration is judged by the content of solid hydrogen-containing fractions in the solvent-treated sample, from which asphaltenes have been removed. The asphaltene concentration is judged by the content of solid hydrogen-containing fractions in the other solvent-treated sample, with the consideration of the defined concentration of paraffins. The concentration of paraffins and asphaltenes in original oil is determined based on the defined paraffin-to-asphaltene ratio in solid hydrogen-containing fractions.