The local temperature, voltage and current nonuniformity in the high temperature proton exchange membrane fuel cell (HT-PEMFC) stack can accelerate the aging of membrane electrode assembly (MEA) and the failure of overall fuel cell stack. This study used micro-electro-mechanical systems (MEMS) technology to integrate micro temperature, voltage and current sensors into a 40 mu m thick stainless steel substrate successfully, and selected the temperature tolerant and electrochemical corrosion resistant polyimide (PI) as protective layer. This flexible micro sensor is characterized by multiple functions, compactness, corrosion resistance, good temperature tolerance, quick response, real-time measurement and optional location. Flexible micro sensor embedded in the high temperature fuel cell stack, the effect on the performance of fuel cell stack was less than 1%. This study used NI PXI 2575 data acquisition unit for real-time microscopic diagnosis of local temperature, voltage and current information at 150 degrees C operating temperature and constant current (5, 15, 30 A) inside the high temperature fuel cell stack, and found that the nonuniform temperature distribution in the fuel cell stack resulted in nonuniform voltage and current distributions and hot stack. (C) 2017 Elsevier Ltd. All rights reserved.