The direction of soil water flux is a key parameter in saturated soil flow fields. Soil texture significantly affects pore connectivity, which introduces randomness into the direction of water flow. Therefore, measuring water flux direction requires consideration of an appropriate spatial scale. The direction of saturated soil water flux can be determined by combining the ratio method with the principle of vector composition. Based on the above requirements, a penta–needle heat pulse probe (PHPP) was designed to measure water flux magnitude in any two mutually perpendicular directions within a plane and to determine flux direction through vector composition. Experiments were conducted in saturated sand, sandy loam, and silt loam, with each soil type repacked three times. The experimental results showed that the accuracy of this method in measuring soil water flux direction was significantly influenced by soil texture. For fluxes greater than 4 cm/h, the mean absolute percentage errors (MAPE) of angle measurements in sand, sandy loam, and silt loam were 4.96%, 6.18%, and 15.06%, respectively. This indicated that the accuracy of water flux direction measurements was decreased with finer soil texture. Compared with fluxes below 4 cm/h, the standard deviations of angle measurements in sand, sandy loam, and silt loam were decreased by 10.40°, 6.65° and 6.71°, respectively, for fluxes above 4 cm/h. This indicated that the accuracy of water flux direction measurements was improved with the increase of flux. Stable water flux angle measurements, with absolute errors below 7.5°, were achieved in sand at fluxes above 6 cm/h and in sandy loam above 3 cm/h, but not in silt loam. These findings suggested that pore connectivity in packed soils varied with texture under different fluxes and hydraulic gradients, thereby affecting measurement precision. Additionally, the geometric relationship between soil particle size and probe spacing affected the measurement accuracy of the ratio method. Optimizing the probe spacing of the PHPP based on soil particle size distribution may improve the reliability of water flux angle measurements by using the vector composition method. These findings can contribute to the development and practical application of heat pulse technology.