In the present study, flow boiling experiment using ITO transparent heating method and LBM simulation by improved Shan-Chen model are conducted to confirm Marangoni effect on the bubble departure and CHF in subcooled flow boiling heat transfer of pure water and CTAC/NaSal(1:1) solutions. Tests are performed with the same tube of d = 2.6 mm, inlet fluid temperature of Tin = 80 °C and outlet pressure of Pout = 101.3 kpa. With high speed camera and microlens, the bubble departure process and flow patterns are recorded at different mass velocities, concentrations and gravity direction. The improved Shan-Chen model with large density ratio(ρl/ρv = 36.55) is applied to simulate the bubble departure process with changing gravity direction and top wall temperature. The present results show that CHF of pure water is increased to approximately 131% by surfactant additives at 100 ppm(CMC), the dry spot at the bottom of bubble causes CHF in pure water and the slug bubble appearing is the main reason of CHF in CTAC/NaSal solution. Due to the solutal Marangoni effect, bubble group in CTAC/NaSal solution is adsorbed at the heating surface which increases the bubble departure diameter. For the first time, the failure of Marangoni effect on flow pattern at CHF is discovered due to the bubble adsorption.