A 3D semi-automatic assembly and adhesive dispensing system was designed and constructed for assembling and bonding the trans-scale parts of micro-tube and micro-sphere together in a three-dimensional space. The system mainly consists of a stereo microscope, two zoom microscopes, a Light Emitting Diode(LED) backlight, a pL class glue dispenser, three micromanipulators and three micro-part grippers. A method to transform the magnification of the zoom microscopes was adopted to detect the trans-scale features of the micro parts from several millimeters to several micrometers. An assembly and adhesive dispensing strategy based on people guiding and micro visual servo technology was proposed and used to align, insert and glud the trans-scale micro parts together fast and accurately. The assembly experiment was carried out by the developed system to validate the method and assembly accuracy. The experimental results show that the position alignment error is less than 1 μm and the pose alignment error is less than 0.5°。The system assemblies and bonds the micro-tube without diameter of 10 μm and the micro-sphere with a hole diameter of 12 μm together and meets the requirements of assembly accuracy and success rates.