Soil compaction is a big limitation to food production in agriculture. Wood ash is an agro-industrial residue generated by the burning of biomass in boilers for energy production. It can be used as a corrective agent and fertilizer of the soil. In this context, the objective of this study was to evaluate the root system of safflower cultivated under bulk density levels and wood ash doses in dystrophic Oxisol. The experiment was conducted in a greenhouse with a randomized block design under a 5x5 factorial scheme composed of 5 wood ash doses (0, 8, 16, 24, 32 g dm-3) and 5 bulk density levels (1.0, 1.2, 1.4, 1.6, 1.8 Mg m-3) with 4 replicates. The soil was collected from 0-0.20 m depth layer. Later it was incubated with the respective wood ash doses. Each experimental unit consisted of a pot made of three PVC (polyvinyl chloride) rings, in which the layers of 0.1-0.2 m were compacted. At 75 days after emergence, the plants were cut, their roots washed and the volume and dry mass checked. The results were submitted to analysis of variance and subsequent regression test, both at 5% probability. Soil densities negatively influenced the root system development and culture of safflower. Application of wood ash doses of 20 to 24 g dm-3 significantly improved root development of plant.