Wall-climbing robots have been widely used in fields of inspection, building cleaning, welding, and so on. These robots can freely move on surfaces with various inclinations, e.g. vertical walls and ceilings. In addition to fundamental locomotion (e.g. wheels, tracks and legs) for robot mobility, a wall-climbing robot must counter the force of gravity for firmly adhering to the inclined work surface by employing adhesion mechanisms (e.g. vacuum suction, magnetic adhesion, etc). In the past decades, various adhesion and locomotion mechanisms have been developed for wall-climbing robots. In practical applications, one of the greatest challenges for wall-climbing robots is to develop optimum adhesion and locomotion mechanisms which enable wall-climbing robots to freely move on various types of complex shaped structure surfaces with various inclined walls, such as milk tanks, ventilation ducts, and so on. This study aims to design and develop a compact and reliable wall-climbing robot with high mobility on complex shaped walls, such as passing 90 convex and concave obstacles with any inclination regarding the gravity, for the inspections of ducts, tanks, bridges, etc. Firstly an overview of the state-of-the-art of the research and development of wall-climbing robots around the world is given. The advantages and disadvantages of various adhesion and locomotion mechanisms are comprehensively discussed for wall-climbing robots for different applications. A modular wall-climbing inspection robot is proposed. The modular design allows the robot to be easily scaled by changing the number of wheeled modules to be joined together. The active joint is able to fold the robot modules to pass various obstacles. General-purpose vacuum suction is employed to enable robot to adhere to various (e.g. metal, wood, glasses, concrete and plastics) structure surfaces. A two-module wall-climbing robot prototype was developed by using SolidWorks. Mechanic design and kinetics analysis of a two-module robot are presented. Comprehensive simulations demonstrate that the proposed wall-climbing robot is capable of freely moving on complex shaped walls. Furthermore, for ferromagnetic structures (such as ships, bridges, steel tanks, and so on), the modular wall-climbing robot with magnetic adhesion is investigated. Compared with general-purpose vacuum suction, magnetic adhesion offers an energy-saving and reliable adhesion solution. Mechanical design and kinetics analysis of a two-module robot with built-in electromagnetic adhesion are given. Simulations validate such an alternative robot design. The major contributions of this thesis include: A modular wall-climbing inspection robot is proposed. The advantages of the proposed robot include high mobility on complex shaped walls, simple structure, easy control, good reliability, low cost, and being scalable. Two types of two-module wall-climbing robot prototypes with different adhesion mechanisms are designed and developed. The robot with general-purpose vibration adhesion mechanism is applicable to the climbing of various structure walls, while the robot with electromagnetic adhesion mechanism offers an optimal climbing device for ferromagnetic walls. Comprehensive design, kinematic analysis and simulations of the two-module wall-climbing robots are successfully completed.