A large number of studies have confirmed the frequent occurrence of plasma irregularities in the mid-latitude ionospheric trough, but there is little understanding of the distribution characteristics about this feature. Based on Swarm in situ plasma measurements from 2014 to 2020, the diurnal, seasonal, solar activity and geomagnetic activity variations of the occurrence rate of mid-latitude trough region irregularities are analyzed. The results show that for the irregularities with scale size of 7.5-75 km: (1) Both of case and statistical analysis indicate that geomagnetic activity has an obvious inhibitory effect on the formation of irregularities in the mid-latitude trough region, whether on the dayside or nightside. (2) The occurrence rate of mid-latitude trough region irregularities during the day is significantly higher than that at night, and the difference between day and night is significantly greater than the difference between the two walls at the same local time section. (3) On the dayside, the highest and lowest occurrence rate appears in winter and summer, respectively; but on the nightside, the highest and lowest occurrence rate appears in equinoxes and winter, respectively. (4) On the nightside, it shows lower occurrence rate under high solar activity conditions, but no obvious solar activity effect is shown on the dayside occurrence rate.