The production process of (C₂–C₄) low molecular weight olefins as a result of  thermocatalytic conversion of the fraction heavy gasoil of catalytic cracking (HGCC) and its mixture with cottonseed oil in the temperature range of 550–700⁰C has been investigated. It is faund that at  result the  thermocatalytic conversion of pure HGCC fraction at 700⁰C, the increase of 16.1–16.4 and 6.3–6.1% have been recorded for the yield of ethylene and propylene respectively. When 10% of cottonseed oil is added to this fraction in the presence of  Omnikat-210P and Omnikat-210P/halloysite mixture catalysts in 700⁰C, 3–2.8 and 0.6–1.4% of mass increases have been observed for ethylene and propylene respectively.