The invention discloses a construction method for full-closing treatment of a contaminated site. The construction method comprises the following steps that the contaminated site containing pollutantsis leveled, and four side edges around the contaminated site serve as closed construction areas; cement soil liners are constructed on the two opposite side edges in an oblique-inserting grouting mode, and the two cement soil liners intersect on the lower part of the contaminated site; cement soil stirring piles are constructed on the other two side edges, and the cement soil stirring piles intersect with the two cement soil liners; and concrete is poured at the top of the contaminated site for top closing treatment, and closing construction is completed. According to the construction method,the pollutants can be isolated in time, the method is simple, the speed is high, and the efficiency is high.