A　temperature　measuring　device　based　on　MAX6675　is　composed　in　this　paper,　primarily　containing　the　temperature　measuring　module,　the　main　microcontroller　unit　(MCU)　and　the　upper　computer.　MCU　collects　the　digital　signal　from　the　temperature　measuring　module　which　consists　of　type-K　thermocouple　and　MAX6675,　and　displays　the　temperature　value　on　a　liquid　crystal　display　(LCD).　When　the　temperature　value　is　higher　than　the　threshold　value,　the　alarm　module　will　work.　By　using　the　RS-485　communication　module,　MCU　transmits　the　temperature　signal　to　the　upper　computer.　At　the　same　time,　the　temperature　variation　curve　is　displayed　on　the　upper　computer　and　historical　data　restored　by　Excel　so　that　it　can　be　monitored　and　analyzed　easily.　PROTEUS　is　used　to　verify　the　probability　and　feasibility　of　the　operating　principle　and　the　correctness　of　the　communication　between　MCU　and　the　upper　computer.　The　temperature　measuring　device　is　verified　by　tests　on　air　conditioning　contactors.　The　device　can　measure　temperature　of　heating　elements　in　real　time　which　is　convenient　and　has　a　wide　measuring　range.