Abstract: Qualifying assessment model by Kent enhancing index is based on Kent's scoring method and constructed through integrating historic data, experts'experiences and probabilistic risk, which has prominent advantages in risk assessment for pipelines. The basic theory of the model is similar to that of probabilistic risk assessment, i.e. risk value equals to the arithmetic product of failure probability and failure consequence. The failure events and conditions of the model are generally identical to that of Kent scoring method. The function of failure probability is composed of exposure, delay measures and adaptive capacity. All the failure mechanisms are defined as two types, time dependent and time independent. Absolute failure consequence is expressed with the cost loss. The main calculation steps are sequentially taken as determination of various leakage aperture probabilities, partition of critical distance for danger zone, confirmation and numerical statement of damage type and failure probability of receptors in danger zone. Case calculation indicates that this feasible method can reduce qualitative indexes. It is an effective and innovative model for pipeline quantifying risk assessment technique.