Algae pyrolysis in alkaline molten salt (AMSP) is a promising method for hydrogen production. This study investigates the transformation of pyrolysis products, focusing on hydrogen yield and purity. Algae pyrolysis in molten NaOH-Na₂CO₃ produces a high hydrogen yield of 71.48 mmol/g-algae in continuous operation. The process involves the conversion of linear alkenes into aromatic compounds, increasing hydrogen production. However, the decarbonation of Na₂CO₃ and deoxygenation of NaOH lead to methane release, reducing hydrogen production. Heavy compounds polymerize at higher temperatures, forming higher molecular weight and unsaturated compounds, while releasing hydrogen. Char reacts with molten salt to form hydrogen and disappears at 650°C, while aromatics in light compounds condense into heavy compounds, forming soot-like at 600°C, releasing hydrogen. The study proposes strategies to improve hydrogen yield and purity by optimizing the AMSP process. The results show that the AMSP process produces a high-purity hydrogen gas with a yield of 72.14 mmol/g-algae at 750°C. The transformation pathways of pyrolysis products in molten NaOH-Na₂CO₃ are proposed, highlighting the role of molten salt in promoting cyclization, aromatization, and cracking of compounds. The study also discusses the properties of light and heavy compounds in bio-oil, their transformation, and the effects of temperature on their composition. The findings suggest that AMSP is a promising technology for hydrogen production, with potential for further improvement through optimization of the process parameters.Algae pyrolysis in alkaline molten salt (AMSP) is a promising method for hydrogen production. This study investigates the transformation of pyrolysis products, focusing on hydrogen yield and purity. Algae pyrolysis in molten NaOH-Na₂CO₃ produces a high hydrogen yield of 71.48 mmol/g-algae in continuous operation. The process involves the conversion of linear alkenes into aromatic compounds, increasing hydrogen production. However, the decarbonation of Na₂CO₃ and deoxygenation of NaOH lead to methane release, reducing hydrogen production. Heavy compounds polymerize at higher temperatures, forming higher molecular weight and unsaturated compounds, while releasing hydrogen. Char reacts with molten salt to form hydrogen and disappears at 650°C, while aromatics in light compounds condense into heavy compounds, forming soot-like at 600°C, releasing hydrogen. The study proposes strategies to improve hydrogen yield and purity by optimizing the AMSP process. The results show that the AMSP process produces a high-purity hydrogen gas with a yield of 72.14 mmol/g-algae at 750°C. The transformation pathways of pyrolysis products in molten NaOH-Na₂CO₃ are proposed, highlighting the role of molten salt in promoting cyclization, aromatization, and cracking of compounds. The study also discusses the properties of light and heavy compounds in bio-oil, their transformation, and the effects of temperature on their composition. The findings suggest that AMSP is a promising technology for hydrogen production, with potential for further improvement through optimization of the process parameters.