The environmental stability, water-processibility and life-span of black phosphorene (BP) severely limit the application of its electronic devices in aqueous system containing oxygen. We reported the controllable preparation of in-situ reduction and deposition of silver nanoparticles on the BP surface and its amino-functionalized multi-walled carbon nanotubes (NH-MWCNT) nanocomposite. With the addition of both NH-MWCNT and Ag, the BP-based nanocomposite was prepared by ultrasonic-assisted liquid-phase exfoliation and was dispersed in carboxymethyl cellulose sodium (CMC) aqueous solution. The morphology, microstructure, and electrochemical properties of the nanohybrid were characterized. NH-MWCNT-BP-AgNPs showed high environmental stability, good water-processibility, satisfactory life-spans, superior electrocatalytic capacity with enzyme-like kinetic characteristics. The nanohybrid was applied as electrochemical sensors for single/simultaneous analysis of uric acid (UA), xanthine (XT) and hypoxanthine (HX). Excellent voltammetric responses for simultaneous determination in linear ranges of 0.1-800 μM with a limit of detection (LOD) of 0.052 μM for UA, 0.5-680 μM with a LOD of 0.021 μM for XT, and 0.7-320 μM with a LOD of 0.025 μM for HX under optimal conditions. Besides, the developed nanozyme sensor was employed for simultaneous voltammetric analysis of UA, XT and HX in real samples with acceptable recoveries. This work will provide theoretical guidance and experimental support for the preparation and application of two-dimensional materials, nanozymes and sensing devices.