To study the diurnal variation characteristics and influencing factors of soil respiration in farmland and grassland in Bayi District, southeastern Xizang. Taking farmland and grassland in Bayi District, southeastern Tibet as the research object, the PS9000&SC-12 soil carbon flux measurement system was used for in-situ monitoring of soil respiration rate. The results showed that: (1) The daily variation of soil temperature in farmland and grassland showed a rapid warming period from 6: 00 to 13: 00 and a rapid cooling period from 14: 00 to 19: 00. The soil volumetric moisture content shows a period of rapid growth from 8: 00 to 13: 00, while it shows an opposite trend from 21: 00 to 7: 00, and the period of grassland is 23: 00-7: 00. (2) Overall, the daily variation of soil respiration rate in farmland and grassland shows a "unimodal" trend. From the analysis of daily changes, the increase and decrease in grassland are much smaller than those in farmland, indicating that grassland carbon emissions are more stable and less responsive to external disturbances. (3) By fitting the equation, it can be seen that the response of soil respiration rate in farmland and grassland to temperature is more significant than that of soil volumetric moisture content. During the period of soil temperature rise, the maximum soil respiration rate in farmland lags behind the maximum soil temperature by 4 hours, while in grassland it lags by 5 hours. The nighttime changes are basically synchronous, and there is a highly significant positive correlation between soil respiration rate and soil temperature in farmland and grassland at night. In summary, the response of soil respiration rate of farmland ecosystem to the external environment is more sensitive than that of grassland ecosystem, and the soil carbon emission is larger.