The invention discloses a site anti-liquidation design fine treatment method based on the Finn model. The method is suitable for anti-liquidation design of liquefied sites in civil engineering and hydraulic engineering. The method is characterized in that 1, based on the liquidation theory of the Finn model, the computational formula representing liquidation affected reduction factor continuity is provided by studying the relation between the excess pore-water pressure ratio of a site liquidation soil layer and anti-liquidation factors with the excess pore-water pressure ratio of the site liquidation soil layer as the link, and the problem that liquidation affected reduction factor values are obtained in a grading mode, and therefore the leaping degree is large is solved; in this way, conservation or insecurity existing in the 'Code for Seismic Design of Building (GB50011-2010)' can be avoided, and the designing scheme is more reasonable; 2, the concept of 'site excess pore-water pressure ratio' is proposed, the method for quickly computing the 'site excess pore-water pressure ratio' is provided, and then a site liquidation judging result obtained according to the 'Code for Seismic Design of Building (GB50011-2010)' can be checked corrected by grading site liquidation according to the 'site excess pore-water pressure ratio'.