We have measured the thermal conductivity along different directions of the S = 1/2 one-dimensional (1D) spin system Sr2V3O9 in magnetic fields up to 14 T. It has been found that the thermal conductivity along the [10-1] direction, k{appa}[10-1], is
large and markedly suppressed by the application of magnetic field, indicating that there is a large contribution of spinons to k{appa}[10-1] and that the spin chains run along the [10-1] direction. The maximum value of the thermal conductivity due to spinons is ~14 W/Km along the [10-1] direction, supporting the empirical law that the magnitude of the thermal conductivity due to spinons is roughly proportional to the antiferromagnetic interaction between the nearest neighboring spins.
