The explosive spalling behaviour of 15 groups of fibre reinforced ultra high strength concrete(FRUHSC) specimens with cubic compressive strength of 116143MPa was investigated subject to ISO834 standard heating condition. The effect of water binder ratio, porosity, fibre type, fibre content, and dimention of specimens on spalling was investigated. Test results show that the UHSC with water binder ratio of 015 has lower porosity and higher strength than that with water binder ratio of 018 and which is more likely to undergo spalling. The addition of 100% corrugated ultra fine steel fibre in volume, which is intended for improving the ductility of concrete at room temperature， cannot prevent spalling. The spalling of both 100× 200mm specimens and 300× 300mm specimens can be prevented by the addition of 015% polypropylene fibre in volume. No spalling is observed when UHSC with water binder ratio of 0.15 encased steel columns with 050% short steel fibre and 015% polypropylene fibre in volume are subject to loadings in fire condition. The fire tests reveal that the spalling of UHSC in the loaded element can be prevented as long as following the proposed addition of hybrid fibres.