The invention discloses a PET base material back costing technology, and belongs to the technical field of film base material back coating. The PET base material back costing technology comprises technical steps including PVA resin dissolving, coating liquid preparation, filtering, standing defoaming, extruding coating, and drying. In the step of coating liquid preparation, water, a polyurethane resin stock solution, a surfactant, and a PVA resin solution prepared in step 1 are introduced into a stirrer successively for stirring, wherein the adding time interval of each component is controlledto be 5 to 10min, and stirring is carried out at 30 to 50 DEG C at a rotating speed of 40 to 60rpm. The advantages are that: 1, the prepared coating liquid possesses no corrosivity, so that a commonstainless steel container is adopted, and equipment requirement is low; 2, wet coating amount is low (50g/m<2>), drying temperature is low, and energy consumption is low; 3, the coating liquid contains no toxic or harmful substance, no pollution is caused, and the technology is friendly to the environment; 4, operation is simple, excellent comprehensive performance is achieved, coating thickness ranges from 4 to 4.5 micrometers, the viscosity ranges from 11 to 13cP, the surface tension ranges from 30 to 33dyn/cm, the performance is relatively stable, the light transmittance is higher than 64%,the haze degree is lower than 28%, the transmittance is excellent, surface resistance is less than 10E11omega, and antistatic performance is achieved.