The invention provides a production method of sirospun undertwisted yarn weft-knitted fabric through false twisting. The production method includes steps of grey yarn selection, weft knitting, inspection, blenching, dying, softening treatment and setting finish; and is characterized in that the selected grey yarn is 14-30tex, a twist coefficient of the yarn ranges from 240 to 290, untwisting during knitting unwinding must be guaranteed by a twist direction of the yarn, a temperature and humidity regulating process is added between the grey yarn selection and the weft knitting, scutching setting is adopted for single-side weft-knitted fabric in the setting finish process, mismatch amount of selvedge on two sides is reduced during the scutching setting. The production method of the sirospun undertwisted yarn weft-knitted fabric through the false twisting has the advantages that the produced weft knitting products have a very soft touch, walewise deflection of single-side weft-knitted products can be improved obviously, change rate of a walewise deflection angle can be lower than 5%, and change of process flow and technological parameters can improve producing efficiency and quality of the products.