A lattice type derrick of an electric transmission line is formed by connecting a suspension base, a standard knot and a pulley in sequence. The two ends of the standard knot are provided with conical end joints. The standard knot and the end joints are formed by a plurality of joint bodies. Each joint body is made of carbon fiber reinforced resin matrix composite materials, and the adjacent joint bodies are connected through a flange. Each joint body of the standard knot comprises four vertical main pipes which are distributed in a rectangular mode and inclined pipes arranged between every two adjacent main pipes. Each end joint body comprises four main pipes which are distributed in a conical mode and inclined pipes between every two adjacent main pipes. Each flange comprises a rectangular base and inserting pipes arranged in the four corners of the rectangular base, and the main pipes of the standard knot and the main pipes of the end joints are inserted into the inserting pipes respectively to be bonded through glue. The derrick is made of the carbon fiber reinforced resin matrix composite materials and is high in strength and light in weight.