Transmission is one of the most important parameter for optic materials which should be measured carefully as its value is related to optic design and optic material manufacture.Commonly,an optic system works at the ordinary environment,so the transmission value is measured and given under room temperature.However,temperature of optic material in some special application areas,such as the seeker with high speed,will rise significantly.In some cases temperature can reach to several hundred of centigrade degrees,optic characteristic for most infrared optic materials will change greatly under this environment,especially for transmission,which will degrade distinctly with the temperature arising.For example,germanium optic material,which has a transmission of 45%in middle and far infrared waveband in room temperature,is nearly opaque for far infrared waveband and has a transmission of less than 20%in middle waveband when its temperature rising approach to 300℃.Degrading in temperature of window material of the seeker will reduce the infrared signal approaching to the photoelectric detecting system in seeker,thus limit the working space and the specification of the military system.In addition,if the speed of the aerocraft increase more faster,temperature of the window will rising more high,thus optic material may behave to absolutely opaque which will lead to “blind” of photoelectric system in military system and make it losing the working ability.As a result,measurement of transmission of infrared optic materials in high temperature is one of the most important problems to be solved in the development of high speed missile.In order to get the transmission of optic materials in high temperature,an equipment for measuring transmission index of optic material in high temperature is introduced in the paper.A kyptol was used as infrared light source and narrow band filter was used to generate the monochrome light.Two parallel flat reflectors separated the light source into two ways,one was sample beam and the other was reference beam.A chopper was used to modulate the light and a lock-in amplifier was used to detect the infrared light.High precision temperature heater was used to control the temperature of sample material.The equipment has the ability to measure the transmission index of optic material from 1μm to 14μm and the temperature scope from room temperature to 700 ℃.Measurement principle and makeup of the equipment are introduced in the paper.Transmissions of A12O3 and germanium in high temperature were reported in the end.