Abstract: 【Objective】 This study was objectiveto explore the factors affecting blood potassium concentration （BPC） of dairy cows. 【Method】 The BPCwas measured from 222 milking cows in summer and 67 milking cows in autumn in Beijingby a hand-held blood potassium meter. The effects of temperature humidity index（THI）， rectal temperature （RT）， parity， milk stage， blood type and milkingstatuson BPC were analyzedusing a fixed model. 【Result】 The resultsshowed that the BPC measured by hand-held blood potassium meter were in the normal range，the BPC was 2.31~5.13 mmol/L. The BPC when THI>72 was significantly higher than that when THI<72 （P<0.05）. The effect of RT on BPCwas different under different THI range. When THI is between 55~60 and 77~78， BPC increased by 0.7 mmol/L and 0.32 mmol/L for every 1℃ increasein RT，respectively. There was no regression relationship between RT and BPC when THI were 72~76 and 79~88（P>0.05）.Venous BPC （4.01±0.05） mmol/L was significantly higher than arterial BPC（3.81±0.05） mmol/L（P<0.01）. The BPC after milking （4.06±0.05） mmol/L was significantly higher than that before milking（3.76±0.04） mmol/L（P<0.01）. The influence of parity and milk stage on BPC was not significant（P>0.05），whilewith the increase of day in milk， the BPC showed a decreasing trend. 【Conclusion】 The hand-held blood potassium meter can quickly and accurately determine the BPC indairy cows. THI has a significant effect on BPC， and the increase of THI will cause the increase or decrease of BPC. Milking status and blood type have great influence on BPC， which should beexcludedwhen it is analyzed.