The present invention relates to the field of insulated cross arms, and more particularly to a 10 kV antifouling composite insulated cross arm comprising side phase insulators, middle phase insulators and inner phase insulators. The side phase insulators, the middle phase insulators and the inner phase insulators all adopt multistage disc insulators. The disc insulator is installed to be vertical to the ground. The end part of each side phase insulator is provided with a side phase lead fixing head. The end part of each middle phase insulator is provided with a middle phase lead fixing head. The end part of each inner phase insulator is provided with an inner phase lead fixing head. The two groups of the side phase insulators, the middle phase insulators and the inner phase insulators are symmetrically connected to a linear pole of a power distribution line from top to bottom to form a vertical type double-back cross arm structure. Compared with the prior art, the 10 kV antifouling composite insulated cross arm has the beneficial effect that 1) the vertical insulator arrangement design can effectively guide the generation directions of the water flow and the ice pillar, and reduce the short-circuit risk of the water flow and the ice pillar between the lead and the cross arm; and 2) the connection compatibility with the conventional 10kV power distribution linear pole is better.