For the large-scale photovoltaic power station, the cost of collecting power line has a large proportion and the electric energy loss is high due to the high generation price of photovoltaic power, so the selection of economic section is important for collecting power line. Because of the change of technology and economy and the limit of application condition, the economic current density curve in existing electrical rule or code can not satisfy the selection of economic section for collecting power lines. Through parameter updating, the economic current density is calculated, which could provide references for the design of photovoltaic power station.