Ce3+-doped gadolinium-based borosilicate (GBSCx) glass scintillators with ultra-high concentration of 16 mol% were synthesized in ambient atmosphere for future Calorimeter application. The valence state of Ce was preciously controlled in the glass by X-ray absorption near edge structure (XANES) spectrum. With the increased Ce3+ concentration, the NBO/BO ratio decreases notably from 5.15 to 0.56. The GBSCx glass scintillators exhibit the broad photoluminescence (PL) band within 350-550 nm regions, with a maximum PL quantum yield (PL QY) of 60.6%. In X-ray excited luminescence (XEL), the integral intensity of the GBSC2 glass is 18.4% compared to the BGO crystal. Meanwhile, it has the highest light yield of 1043 ph/MeV with an energy resolution of 28.4% at 662 keV under γ-ray excitation. When the doped concentration of Ce3+ exceeds 4 mol%, the proportion of light yield within 1 μs integral gate exceeds 95%, which conforms to the requirement of fast time response. Interestingly, the concentration quenching effect of high concentration Ce3+ (x≤14) does not occur in the glass scintillators under γ-ray excitation. With the increase of Ce3+ concentration, both the fast (100-18 ns) and slow (1000-59 ns) components of scintillation decay time decrease dramatically. Therefore, the developed GBSCx glass scintillators, featured with the reasonable light yield and fast time response, have a promising application in future high energy physics (HEP) experiments.