The invention discloses a construction method of a section-steel triaxial soil-cement mixing pile, comprising the following construction steps: (1) measuring paying-off positioning pile; (2) digging trench; (3) arranging guide positioning section-steel; (4) the mixer taking place, correcting and reviewing levelness and verticality of the pile driver; (5) mixing cement grout, starting an air compressor, and sending the grout to the pile driver; (6) a drill bit spraying grout, gas, cutting soil body and sinking to the elevation of designed pile bottom; (7) the drill bit spraying the grout and elevating to the elevation of designed pile top; (8) vertically lifting the section-steel and positioning the section-steel; (9) correcting and reviewing the verticality of the section-steel; (10) inserting and fixing the section-steel. The pilling process provided by the invention is suitable for cohesive soil with large compression modulus, soft ground layer which is mainly composed of cohesive soil and silty cohesive soil, mucky soil, plain fill and saturation loose sand without flowing underground water; especially for the cohesive soil with large compression modulus, the invention not only can solve the problem that the pre-mixing sinking is difficult, but also can solve the problem that the time of repeatedly-mixing process is too long.