In this paper, we identify the model parameters of flexible supercapacitors from time-domain data using fractional cuckoo search. The time-domain data are five galvanostatic charging/discharging (GCD) curves of reduced graphene oxide-based flexible supercapacitor at different exfoliated-graphene-mediated graphene oxide (EGM-rGO) relative content. These time-domain curves are used the parameters of three well-known supercapacitor models: R_s-CPE, R_p-R_s-CPE, and R_s- C-CPE. The extracted parameters are summarized, and the effect of EGM-rGO relative content is discussed. Based on these discussions, one model is recommended for each EGM-rGO relative content.