We report a study on the heat transport of an S = 1 Haldane chain compound Ni(C_3H_{10}N_2)_2NO_2ClO_4 at low temperatures and in magnetic fields. The zero-field thermal conductivities show a remarkable anisotropy for the heat current along the spin-chain direction (kappa_b) and the vertical direction (kappa_c), implying a magnetic contribution to the heat transport along the spin-chain direction. The magnetic-field-induced change of the spin spectrum has obviously opposite impacts on kappa_b and kappa_c. In particular, kappa_b(H) and kappa_c(H) curves show peak-like increases and dip-like decreases, respectively, at sim 9 T, which is the critical field that minimizes the spin gap. These results indicate a large magnetic thermal transport in this material.
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