Oil sludge is an organic solid waste produced in oilfield exploitation, transportation, and petroleum refineries. Pyrolysis is one of the most effective ways to reduce oil sludge and realize energy re-utilization. In the present work, the amounts and distributions of pyrolysis products at different reaction time and with different amounts of NiO catalyst were investigated with PY-GC/MS. The results suggest that the degree of the pyrolysis reaction increased and more macromolecules were degraded into smaller hydrocarbons as the reaction time prolonged. The addition of NiO catalyst effectively promoted the conversion of aromatic and paraffin products, and increased the production of small molecule olefins.