An improved Network Calculus (NC)-based model is proposed to analyze the upper-bound latency for Time-sensitive Networking (TSN). It aims to address two key issues existing in the benchmark NC model: on the one hand, the inaccurate description of the Arrival Curve (AC) for simultaneously arriving data packets; on the other hand, the design of the network Service Curve (SC) does not consider the interdependencies between nodes. In the simulation experiment section, the pessimism of theoretical analysis is reduced by comparing the two models, and the validity of the improved NC-based model is verified using the OMNeT++ platform.