The invention discloses a production process of an insulating layer of a railway signal cable, and relates to the field of signal cables. The production process comprises the steps of evenly mixing nano titanium dioxide modified polyvinyl chloride with dibutylhydroxytoluene, corundum modified polycarbonate and isoprene rubber, stirring by using a high speed mixer, then putting the obtained mixtureinto a potassium cyanide solution of basic copper carbonate and stirring, centrifuging, drying, and then adding a calcium chloride solution; adding tert-butyl-4-hydroxyanisole, dicumyl peroxide, acetic acid-nitrocellulose and 2-methyl methacrylate in a water bath; finally, adding boron fibers, nano-alumina and methyl methacrylate-n-butyl acrylate-sodium allyl sulfonate, carrying out ball milling,adding sesame oil, fumigating under saturated steam pressure, and sending to an extruder for extrusion molding. The prepared insulating layer is high in strength, good in aging resistance and corrosion resistance, and longer in service life.