The invention discloses a surface sizing technology of high-strength corrugated medium paper. The surface sizing technology comprises the following steps: conveying a sizing starch solution, adding a cationic surface sizing agent, performing surface sizing, and reflowing and recycling a sizing material. In the surface sizing technology, anionic rubbish in the reflowed sizing material is treated and removed, so that not only is reaction between the anionic rubbish and the added cationic surface sizing agent avoided and the using effect of the cationic surface sizing agent improved, but also the problem of accumulation of the anionic rubbish in the reflowed sizing material along with the increase in the number of recycles can be avoided; treatment of the anionic rubbish is simple and convenient, and easy to implement and control; a production process is clean, environment-friendly, pollution-free, and very low in running cost; therefore, the surface sizing benefit is comprehensively improved.