Abstract: K Type thermo-sensitive Cytoplasmic male sterile wheat which was based on two-line hybrid wheat ,could produce hybrid wheat seeds because of its completely sterility in normal wheat growing season of northern China, but fertility restored partly in anti-season seeding . This study has made a more fine research on the fertility-conversion critical period, abortion of pollen development process of KTP116A and K116A by using artificial climate chamber and the smear method. The results showed that KTP116A can carry the normal meiosis and develop into mature pollen grains under fertile environment; but in sterile environment, only a few can go through the second mitosis and produce two sperm cells, most of the them are arrested at binucleate grain, abnormal pollen grains and shell anthers without protoplast; two fertility sensitive periods of KTP116A were from meiosis to early microspore and binucleate to trinucleate, corresponding to 2-8d before heading and the 3-5d before flowering. Temperature sensitive stage is about 10d. These findings will make a foundation to further study of abortion mechanism, aboration reasons analyzing and the better use of TCMS.