Due to the large deviation of material properties and inherent machining tolerance, uncertain factors should be considered for designing and analyzing composite structures. An evaluation method for energy-absorbing characteristics of thin-walled composite structures with uncertain parameters was proposed and developed herein. Thin-walled composite tubes extensively applied on automobile and aircraft are typical crushable elements for absorbing collision energy. The uncertainties due to machining tolerance from thickness and inner diameter of a tube were considered in the present paper and represented by interval model. Triggering Specific Stress (TSS) and Specific Energy Absorption (SEA) are concerned and calculated by Finite Element Analysis for indicating energy-absorbing characteristics of the specimen under quasi-static axial crushing. Response surface method was then used to build a second-order function between uncertain parameters and the two indicators of energy-absorbing characteristics. Interval perturbation of the response surface function was at last performed to establish the interval of TSS and SEA respectively. The results showed that, compared to SEA, TSS is more affected by the uncertainty from wall thickness and inner diameter. In addition, the effect of uncertainty from wall thickness on energy-absorbing characteristics is more significant than that from inner diameter. This investigation revealed that the machining tolerance of composite tube should be limited as low as possible to keep designed energy-absorbing characteristics.