Proton Exchange Membrane Fuel Cell (PEMFC) has advantages that other energy sources don’t have, and recently, it has been spotlighted in many industries such as transportation and power generation. However, although much research has been conducted on PEMFC, studies on operating conditions of bipolar plates in cells have been insufficient. Most of the studies that have been conducted so far are obtained by setting a few points on the edge or the latter line of the bipolar plate when acquiring data such as the operating temperature or relative humidity of the cell, so the research is extremely limited. In order to maximize the performance of PEMFC and preserve its durability, it is very important to control operating temperature and humidity optimally. Typically, water contents inside membrane electrolyte is determined by externally delivered water vapor and electrically reacted water vapor. Since water vapor is delivered and exhausted through bipolar plate, the vapor concentration in the bipolar plate is a clue to understand operating characteristics of PEMFC. Even though vapor concentration is a key to improve the performance, it is very difficult to measure direct distribution on the membrane electrode assembly. Therefore, this study attempted to observe the behavior of vapor flow inside the bipolar plate. By mounting several sensors in the flow path of the bipolar plate, it is possible to measure the temperature and humidity field data in the flow path, so that it is possible to observe the actual operating environment in the stack under various operating conditions and to establish a control strategy. Especially, this approach not only makes it possible to analyze the static water content in a steady state where no change in load occurs, but also enables dynamic observation of transient characteristics in the flow path when the current density changes. Several temperature and humidity sensors were installed on the bipolar plates of the cathode and anode respectively, and reliability and performance evaluations were performed through experiments. Reliability was evaluated by setting up a relatively accurate comparison sensor among the existing sensors that were not used in this study, and analyzed the effects of flow disturbance in the flow path by comparing with the polarization curve in the general cell. After the sensor calibration, an experiment was performed to obtain temperature and humidity data as the current density changed. As a result, it was possible to quantitatively analyze the water content delivered from the outside or generated inside the stack.