Abstract: Firstly,this paper proposes an assumption in which the cause nodes do not affect the result nodes directly,and they only contribute an intensity to the probability distribution of the result nodes,and the status of result node is determined randomly by the accumulation of the contributed probabilities of the nodes involved.Secondly,it introduces the concept of unitizing coefficient to provide the unitizing capability during reasoning process.Finally,it points out that there is a property that we can obtain the same inference consequence supposing that they are mutex among all states of all linkage events pointing to the same node in the multi value causality diagram under the assumption above.The property can ensure all states of any node are mutex one another during reasoning process and hence the reasoning algorithm is simplified.