A mechatronic system is a mixed and multi-domain system. It will typically consist of many different types of interconnected components and elements, which fall within different domains such as mechanical, electrical, hydraulic, thermal and control. Due to the multi-domain nature of a mechatronic system and dynamic couplings and interactions between its components, a multi-domain and integrated modeling approach is required, where all the domains are treated in a unified manner. There are various unified languages for modeling of mixed mechatronic systems, including block diagrams, bond graphs and linear graphs. Among these graphical tools, linear graphs take an important place. This work presents an integrated mechatronic modeling tool using linear graphs and provides a unified language and environment to model different parts from different domains in a unified and integrated model.To demonstrate the capabilities of the presented framework, an integrated model of a complex electro-hydraulic servo manipulator and its governing motion equations in the state space form are presented.Earlier work on the modeling of electro hydraulic servo systems mostly focuses on the separate modeling of the components, and often only linear models have been derived due to the complex nature of these systems. In this thesis we have developed an accurate integrated and comprehensive linear graph model of the considered electro-hydraulic servo system. The system includes a hydraulic power supply unit, a two-stage flapper-nozzle servo valve, a double-acting single-ended hydraulic cylinder, a position transducer (embedded in the cylinder), a controller circuit, and a servo amplifier. The linear graph model of each subsystem is generated from an object oriented point of view, and the full integrated dynamic model of the system is obtained by assembling the linear graph models of the subsystems. The application of continuity and compatibility equations along with the constitutive equations of individual elements leads to a set of fifteen nonlinear first order differential equations as state equations of the mixed system. The present work also proposes general linear graph structures for modeling of operational amplifier circuits and piezoelectric transducers. Based on causality propagation, and after addressing the drawbacks of available approaches in literature, a new algorithm for causality analysis of linear graph models has been presented. Using a systematic procedure, a computer program is developed to the automatic generation of the symbolic state equations of a system starting from its linear graph model. Key Words: Mechatronic systems, Integrated mechatronic modeling, Linear graph theory, Electro-hydraulic servo systems, Causality analysis