We have developed a new theory to measure thermal properties of a soil and velocity vector of water flow in the soil simultaneously. The thermal properties of a soil are thermal diffusivity, k [m²/s], volumetric heat capacity, C [J/(K m³)], and thermal conductivity, K [J/(K m s)], where the third is the product of the former two. The velocity vector of the water flow in the soil consists of the velocity and the direction of the water flow in the soil. The present paper uses a heat pulse generated in the soil. The heater generates heat constantly during a period of t₀ [s] and the total amount of heat generated from the heater is Q [J/m for a linear heater, and J for a point heater]. In the conventional heat pulse techniques, measurements of the thermal properties of soil should be done only with no water flows in the soil. This restriction has limited the use of heat pulse techniques in the site. The present theory provides methods for the measurement of the thermal properties of soil with water flows in the soil. For the measurement of one- or two-dimensional velocity field, a linear heater should be used to produce the heat pulse. Temperatures at two or four orthogonally symmetric positions around the heater should be measured continuously for the measurement of one or two dimensional velocity field, respectively. For the measurement of three-dimensional velocity field, two linear heaters or a point heater should be used. Anyway, temperatures at six orthogonally symmetric positions around the heater should be measured continuously for the measurement of the three-dimensional velocity field. In order to obtain k and C we measure the peak time, t_m [s], and peak value, T_m [K], of temperature rise produced with the heat pulse. The present paper shows a formula that leads a non-dimensional parameter, H=r u/(2 k), from the ratio of difference to sum of the temperatures at a set of symmetric points, where r = distance between the heater and temperature sensor [m], and u = component of velocity vector that is parallel to the temperature sensors [m/s]. For the measurement of a two-dimensional velocity field, for instance, we will get two H's like H_x and H_y corresponding to x and y components of the velocity vector, u_x and u_y, respectively. We call (H_x²+H_y²)^1/2 as H_p. The present paper provides a new analytical solution that leads thermal diffusivity, k, from a ratio of half pulse width to the peak time of the temperature rise, m=(t₀/2)/t_m, and H_p. Now the values of u_x and u_y are calculated from thus obtained values of H_x, H_y and k assuming that the value of r is known with calibration. Finally, the value of C is obtained from T_m and an integral of the well known function for temperature rise produced with a heat pulse. For possible errors in distances, r, between the heater and temperature sensors, the present paper shows methods to cancel the positioning errors. Since temperature of the heater becomes infinity if the shape of the heater is rigorously line or point, cylindrical or spherical heaters should be used in stead, for which we have no analytical solutions. Still, the analytical solutions stated above could be utilized with some amount of errors according to the finite radius of the heaters, which is to be lead to numerical calculations.