A PV standalone system in traffic signal application was researched and designed based on the energy shortage worldwide and to settle some problems on traffic signal lights against actual application. This system was able to leave out the construction project of the road, economization of funds, energy saving and environmental protection, and which will not result in the traffic jam in the process of fixing and debugging. The traffic control conveniently becomes true at the area where is far away from the grid. The main aim of the thesis is to design a PV standalone system in traffic light application in Shenyang, China. Additional aim is to find the most energy-efficient ways of working for LED load in solar PV lighting application. The PWM technology was studied and the energy consumption under different conditions will be tested. The system design feeds the relevant industry standards. The method for system sizing is used extensively by Telecon in Australia and represents a very conservative approach in which array size is optimized as a function of battery capacity. Through theoretical and practical research, a multi-view understanding can be gained in the PV application. A standalone system in traffic signal is sized and the results of sizing are 275W PV panel and 390Ah battery totally. The system includes three same systems with the sizing of 55W PV panel and 80Ah battery and one bigger system with the sizing of 110W PV panel and 150Ah battery. The required capital cost is ?25770. The discount payback is 17.1 years. The saved electricity per year is 151.8KWh. A cost effective system could be gained with the increased intensity of financial incentive and decreased price of PV panel.