The invention discloses a method for solidifying and sizing gel-spun fibers in a production process of ultra-high molecular weight polyethylene (UHMWPE) fibers. Cooling and sizing fluid in a cooling and sizing groove (3) is prepared from a lower phase separation accelerator (5) and an upper water seal (4), wherein the upper water seal (4) is used for cooling and sizing the gel-spun fibers; the lower phase separation accelerator (5) is used for accelerating phase separation so as to prompt paraffin oil on the surfaces of the gel-spun fibers to be separated out in an accelerating way, and forming porous and reticulated UHMWPE compact layers on the surfaces of the gel-spun fibers so as to increase the strength and initial modulus of the gel-spun fibers, enable the fineness consistency of finished products to be high and reduce strength fluctuation; the paraffin oil is separated out from the gel-spun fibers and is then dissolved in the phase separation accelerator so as to form lower mixed liquid, and the density of the lower mixed liquid is controlled to be greater than 1.1g/cm<3>; the gel-spun fibers are discharged out of the cooling and sizing groove (3), and the oil content of the gel-spun fibers is controlled to be within a range of 50-85%. After the structure is adopted, the method has the advantages of being simple in structure production process line, convenient in production and processing, high in strength and modulus, low in fineness dispersion, good in product performance consistency, and the like.