Abstract: A real time temperature measurement system with InGaAs/I is introduced at first.Then measures to improve the accuracy are discussed.The first is to select the detector,optimize modulation disk and amplify the signal with selective frequency.The second is to place a narrow band filter between modulation disk and the detector.The third is to use water cooling shelter and take electrical compensation.The fourth is to improve the sampling accuracy of the system.At last some relative analyses and discussion are put forward.