In this experiment, nanocrystalline Y 3 Ba 5 Cu 8 O 18 superconductor powder was prepared by citrate–nitrate auto-combustion reaction. A series of Y 3 Ba 5 Cu 8 O 18 precursor gels with different citrate–nitrate ratio ranged from 0.3 to 1.0 have been prepared by varying the amount of citric acid added. The auto-combustion reaction during drying process transformed the precursor gels into ashes powder that upon calcinations at 900°C yield Y 3 Ba 5 Cu 8 O 18 nanocrystalline powders. The TG/DTA analysis reveals that the precursor gels with 0.3⩽c/n<1.0 decomposed in a single-step reaction combusted at temperature of around 230°C. Established from XRD and SEM characterization, the Y 3 Ba 5 Cu 8 O 18 calcined powder prepared from c/n=0.7 precursor gels has got the orthorhombic structure with smallest particle size (∼10nm) compared to the rest of the batches. Samples with c/n=0.5 and 0.7 appeared in this work to be electrically superconducting at temperature above 100K as measured using standard four-probe technique. This emphasized on maintaining a stoichiometric or near stoichiometric reaction for the analysis.