Abstract: This paper is to analyze multiaspects and multiseries in petroleum accessment, and to study the undeterministic knowledge and qualitative laws used by petroleum geologists and to conclude that there is the potential information loses in the processes of thinking and description. It is important to make extensive investigation about the knowledge structures and thinking peculiarities of the experts, and to sum up the qualitative laws and message transmition, which would be helpful for petroleum geology in the extent of qualitative description of mere experience toward more scientific description combined with qualitative and quantitative methods; and which would be useful in introducing new ideas and methods for the development of petroleum geology.