Manufacturing method of K-shaped derrick of high-position backward folding type petroleum drilling machine

The invention discloses a manufacturing method of a high-position backward folding type K-shaped derrick of a petroleum drilling machine, the uppermost end section of the derrick adopts an integral welding truss structure, a rotating point lug plate hole at the backward folding position is integrally processed, all the other derrick sections are manufactured by adopting an existing method, and a connecting frame, a back cross beam and an inclined supporting rod for connecting the left section and the right section are independently manufactured; all the sections of the manufactured derrick are connected through a tool support, and all the sections of the derrick are sequentially and horizontally installed and connected from bottom to top; the machined uppermost section is used as the standard, the connecting lug plate of the section connected with the uppermost section is welded in a matched mode, relevant sizes are detected, proper adjustment is conducted, and after the requirement is met, the other inclined