In recent years, although there are several interesting colorimetric methods developed for the detection of silver ions (Ag+), the simple, sensitive, real-time and quantitative sensing platform is still lacking. Herein, by using Ti3C2Tx MXene nanoribbon (Ti3C2TxNR) as the carrier, gold@platinum (Au@Pt) bimetallic nanoparticles were firstly decorated on the Ti3C2TxNR surface via a facile self-reduction method, and the formed Au@Pt-Ti3C2TxNR nanohybrid can catalyze effectively the oxidation reaction of 3,3',5,5'-tetramethylbenzidine (colorless) to generate blue substance (oxTMB), displaying prominent peroxidase-activity. In the presence of Ag+, it can pose remarkable inhibiting effect again the catalytical activity of Au@Pt-Ti3C2TxNR and stop the generation of oxTMB. Based on this, the as-obtained Au@Pt-Ti3C2TxNR nanozyme was then introduced to construct a novel colorimetric sensing platform of Ag+ with low detection limit (1.57 nM) and wide linearity (5.0 nM - 9.0 μM). In addition, by combining the unique advantages of the hydrogel and smartphone, a simple, real-time and quantitative platform of Ag+ monitoring was also constructed, exhibiting important applications for Ag+ detection.