With the rapid development of globe solar photovoltaic industry, performance testing and evaluation of solar modules have been largely concerned, while the primary basis of evaluations is the electrical performance of modules, namely the voltage - current characteristic curve. Nearly module’s conversion efficiency which defined as its maximum electrical power (Pmax) divided by the total incident photon power (Pin) became more and more valued, because higher efficiency means lower cost. Generally, electrical performance parameters of the modules need to test under standard test conditions (STC), but STC can only be simulated in laboratory-controlled environment while solar modules actually work under natural sunlight outdoors, To solve this problem we propose researches on outdoor testing of solar modules to investigate the electrical performance parameters of solar modules in a variety of environmental conditions. Also, according to the results, we will analysis the impact of various environmental factors on the performance of solar modules, including radiation spectrum, Incident angle, temperature, wind speed, and wind direction. In addition, we can analyze the difference between the performance parameters result of outdoor and indoor test and its main reason.