¡@¡@Because of the poly-si thin film transistor have the advantage of high mobility, it can improve the analysis for the flat plan display. Using the above advantage can combine the integrated circuit as control IC and memory on the small panel to reduce the number between the switch circuits and the outside contacts. These precise circuits must be considering the photo current¡Bthermal effects and the parasitical capacitance more due to the influence of these precise circuits is more serious than the switch circuits. In my thesis, the research of the electrical characteristics of the newest excimer laser crystallize coplane poly-si thin film transistors ,and using the device length with width is 128um/6um and 128um/16um can be extracted that the environment of the facing illumination have the photo-leakage current than none illumination about four orders, and the photo-leakage current is not consider with any gate voltage. ¡@¡@With the discussion of the capacitance, the main point of my researches is to change different conditions to extract the gate to source capacitance (Cgs). In addition, the slight carriers may effect the devices with the high mobility system on panel (SOP) technology error, the temperature must be considered. ¡@¡@We find the mobility is bigger at the environment of the temperature is 300K than the environment of the temperature is 100K when the device work in the linear region and the on current is lower at the environment of the temperature is 300K than the environment of the temperature is 100K when the device work in the saturation region. Using some references and some models as the concepts can analysis some phenomenons I refer to above.