In this paper，optical devices incorporating beam splitter are utilized to design the split-folding light path and

solve prominently the low definition problem of the traditional light path. Meanwhile，the ghost interference is eliminated

by virtue of vertical reflection. Based on the optical path and MATLAB software，the knife-edge optimization

is actualized. Through the calibration experiment realized by blowpipe，the function between temperature and the

gray value of schlieren image provides a contactless solution to measure the airflow temperature，together with the

visualization system of gas temperature field.