Abstract: This paper presents a novel and robust blind watermarking algorithm for 3D parametric process plant models based on an improved logistic chaotic system.Instead of modifying the CAD model's geometry or topology information,which is mostly used by existing algorithms,our approach embeds the watermarks into the model's dual points by making full use of the model's topology information.Group operation of dual points is processed based on the improved logistic chaotic system,and the same information is embedded into the points of the same group by slightly modifying the point's size.The watermarks can be blindly extracted according to the relationship between the sizes of each pair of dual points.Theoretical analysis and experimental results show that the algorithm can resist many attacks such as cropping,adding,scaling and mesh simplification without modifying the model's geometry and topology information.