Simultaneous monitoring multiple drug delivery with different drug ratios can obtain the real-time relationship between drug ratios and therapeutic effects, which can accelerate the composite drugs development for some uncertain epidemics. We introduce a method of constructing flexible inorganic core-shell nanofibers with tunable multicolor upconversion fluorescence to satisfy the demand of simultaneous monitoring. The tunable green to red ratio varying from 5 to 0.3 is obtained by proposed pretreatment followed by reoxidation process, which need not to change chemical constituents or concentrations thereby would not bring about disadvantageous fibrous morphology and bad spinnability. Compared with traditional method that cannot monitor dual drug delivery and show a low sensitivity, the nanofibers prepared by our new method exhibit a high sensitivity verified by simultaneously monitoring dual drug delivery with multiple different drug ratios. Due to the tunable green to red ratio and appropriate selection criteria, these nanofibers exhibit a broad detection range of two drugs without losing excellent sensitivity, which cannot be achieved by conventional single-drug monitoring system.