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Soil temperature influences crop growth and its grain formation in high altitude cold region. Field plot experiments were conducted in order to investigate the effects of straw mulching on tillage soil temperature and the grain yield of spring highland barley in high altitude cold region of Tibet, China. Four experimental treatments, including straw mulching application rates of 0 (control), 5 000 (M1), 10 000 (M2), and 15 000 kg/hm 2 (M3), were designed. The results showed that straw mulching on soil surface could adjust soil temperature significantly. Compared with the control treatment, average daily soil temperature was lowered by 2.8~3.9℃ at seedling stage but it was raised by 0.4~1.8℃ at other growth stages of spring highland barley after straw mulching application. Straw mulching significantly reduced plant height (2.29%~16.53%) and dry matter weight (3.98%~25.93%) at seedling and jointing stages, but it increased plant height and dry matter weight by 3.12%~10.31% and 2.17%~18.26% at the filling and mature stages of spring highland barley, respectively, and it significantly decreased root mass density in 0~20 cm soil layer, but it was increased in other soil depths. Straw 〖JP2〗mulching significantly increased the thousand seed weight (4.65%~13.95%) and grain yield (4.30%~〖JP〗13.50%) of spring highland barley. To a certain extent, straw mulching also lowered the spike length and the grain number in each spike of spring highland barley. Generally, there was no significantly statistical difference among different straw mulching application rates (M1~M3) in soil temperature, but significant differences existed among M1~M3 in the growth parameters (except ear length and seeds per ear) of spring highland barley. Straw mulching is advantageous to the thriving growth of seedlings and the increase of grain yield of spring highland barley.