This study reports the spray characteristics of two fast pyrolysis bio-oils with different viscosities (0.0753 and 0.1522 Pa.s at 21 degrees C) and a set of bioslurry samples prepared from the bio-oils at various biochar loading levels (5, 10, 15, and 20 Wt %). Two types of atomizers (impact atomizer and two-fluid atomizer) were used. Experiments for the impact atomizers of various sues were carried out at injection pressures of 2:07-4.96 MPa and feeding rates of 108-490 mL/min. At a constant pressure, the Sauter mean diameter (SMD) of bio-oil and bioslurry increases as the flow number increases, while at a constant flow number, the SMD decreases rapidly with increasing pressure. The biochar loading level has a significant impact on the bioslurry atomization characteristics. An increase in biochar leading level results in a substantial increase in the spray SMD. Experiments using the twin-fluid atomizer (N-2, as the atomization gas) were carried out at flow rates Of 2-6 mL/min. A twin-fluid atomizer is more applicable at considerably lower liquid flow rates than an impact atomizer. The spray SMD of the twin fluid atomizer is mainly influenced by the liquid viscosity, gas/liquid ratio (GLR), and biochar loading level. An increase in viscosity and biochar loading level leads to an increase in the spray SMD, while an increase in GLR leads to a reduction in the SMD. Correlations have also been developed to predict spray SMD of bio-oil and bioslurry using both atomizers.