Liquid trapping damage has always been considered as an important reservoir damage mechanism of tight sandstone gas reservoirs. The degree and mechanism of the liquid trapping damage of ultra-tight sandstone gas reservoirs vary with different physical characteristics and working fluid types of reservoirs. In this paper，we studied the ultra-tight sandstone gas reservoirs in the Tarim Basin. The evaluation method simulating the four stages of drilling-drill stem test-killing operations-completion testing was proposed to test the comprehensive liquid trapping damage induced by the sequential contact of oil-based/organic salt drill-in fluid filtrates-organic salt completion fluids. The typical matrix and fractured samples were selected. The results showed that the permeability damage rates（PDRs）of comprehensive liquid trapping of the matrix sample treated by the sequential contact of oil-based/organic salt drill-in fluid filtrates-organic salt completion fluid were 86.00% and 98.37%，respectively. The corresponding two parameters of fractured samples were 99.95% and 63.45%，respectively. Analysis indicates that the special clay mineral types，occurrence，and narrow throats of ultra-tight sandstone gas reservoir cause oil-based drill-in fluid filtrates to suppress the intrusion of the subsequent water-based working fluids for the matrix sample. That the remaining oil-based drill-in fluid droplets in the fractures obstructing the flowback and evaporation of the organic salt completion fluid during the subsequent flowback process is the main mechanism for the oil-based drill-in fluids’mitigating the comprehensive liquid trapping damage of matrix and aggravating the comprehensive phase trapping damage of fractures.