The daily sap flow velocity of wheat was measured using Dynamax Flow 32 and the environmental factors were monitored using Automatic Weather Station System at the jointing and flowering stages. The relationships between sap flow velocity and environmental factors were also analyzed. Results showed that (1) the curve for diurnal variation of sap flow had a peak. The trend was the same at jointing and flowering stages. Sap flows at the two stages started at 7:00-8:00 and 6:00-7:00, respectively. The maximum sap flow velocity was observed at 12:00-14:00, and the values were 1.90 and 2.66 g/h (24th and 25th, April, sunny day, jointing stage) and 3.39 and 2.96 g/h (0518 and 0519, sunny day, flowering stage), respectively. Then the sap flow velocity dropped down to the lowest at 21:00 and no sap flow was observed at night. The value of sap flow on sunny day was higher than that on cloudy day. (2) There was a similar trend between sap flow velocity and environmental factors. The relationships among them were significant. There was a negative significant correlation between sap flow velocity and humidity, while it showed positive correlations with other environmental factors. From correlation analysis, their coefficients were in the order of photosynthetically active radiation > air temperature > humidity > wind speed.