The Thermal Dissipation Probe (TDP) method was used to conduct long-term continuous observations from February 2012 to March 2014 on the sap flow velocity of Acer wangchii in karst regions. In addition, environmental factors including air temperature (Ta), relative humidity (RH), solar radiation (Solar), wind speed (WS), rainfall, soil water content (SWC), and the characteristics of A. wangchii sap flow were investigated, and correlations between environmental factors and different temporal scales were determined. The findings revealed the following:1) sap flow velocity in relation to different weather conditions, in descending order, was sunny, cloudy, and rainy days, and the sap flow was generally high in the daytime and low at night; 2) the average amount of sap flow was 5.08 kg/d, with the sap flow quantity varying in different seasons, in descending order of (8.38 ±5.32) kg/d in summer, (5.16 ±3.99) kg/d in autumn, (4.86 ±3.77) kg/d in spring, and (1.94 ±1.40) kg/d in winter; 3) the monthly sap flow was 153.64 kg and the annual sap flow was 1838.40 kg, on average; 4) on the hourly scale, solar radiation over 1 day was the main environmental factor influencing sap flow regardless of the weather conditions, while the influence of the other environmental factors on sap flow varied in the daytime, at night, and in different seasons and rainfalls; and 5) over 1 year:on the hourly scale, 63.50% of the sap flow could be interpreted jointly by the environmental factors including solar radiation, Ta, RH, SWC_10cm and WS. On the daily scale, 68.50% of the sap flow could be interpreted jointly by the environmental factors including solar radiation, Ta, SWC_10cm and rainfall. On the monthly scale, the sap flow quantity could be interpreted with the single environmental factor, Ta, which contributed 74.80% to the total. With the time scale reducing, the more environmental factors were involved in the regression equation, the lesser interpretation of sap flow quantity (R²) would be. In comparison to similar findings from other regions, the impact of environment factors on sap flow diverged greatly. However, on temporal scales, solar radiation or PAR and Ta were the two major factors that affected sap flow, and no environmental factor contributed in the interpretation of sap flow on rainy days, which is consistent with the present study. Therefore, estimates of the impact of environmental factors on sap flow on rainy days deviate, and particular attention should be paid to the role of soil water content.