The utility model discloses a straight line iron tower for a 330kV electric transmission line in a more thunderstorm region and a heavily polluted region, which comprises a tower body and a cross arm, wherein the cross arm is fixedly arranged at the top of the tower body, the cross arm is a truss structure, a chord member and a web member of the cross arm respectively comprise an insulating inner core and an insulating outer layer, an interlayer is formed between the insulating inner core and the insulating outer layer, and the interlayer is filled with insulating filling agent. When in use, as the cross arm is made of insulation material, compared with the normal like iron tower, the straight line iron tower not only has characteristics of light weight, high mechanical strength, impact resistance, corrosion resistance and heat resistance, and the like, but also can effectively improve the pollution flashover-proof performance and the lightning-proof performance of the iron tower, and guarantee a transmission system to run with safety, stability and energy saving.