Herein, we report a new process for intensified hydro-upgrading of a biocrude produced from the hydrothermal processing of Auxenochlorella pyrenoidosa (AuP) in tetralin at a mass ratio of 1:1 with the addition of 10 wt.% Pt/C and 8 MPa H2 at different temperatures (300-480 °C) and times (1-8 h). Under the selected reaction conditions, the gaseous products were replaced with fresh H2 at regular time intervals; this process was then continued until the total reaction time was over. Increasing the number of H2 replacement times decrease the C, N, O, and S contents and increased the H content. The treated bio-oil mainly consisted of aromatic, saturated and unsaturated hydrocarbons. Overall, H2 replacement removed some of the denitrogenation, desulfurization, and deoxygenation products and avoided secondary reactions of gaseous products with the bio-oil, thus promoting the hydrogenation reaction and N, O, and S removal from the treated bio-oil.