The invention provides a composite insulating cross arm. The composite insulating cross arm comprises an insulating core body, an outer sleeve, a first connection mechanism and a second connection mechanism, wherein the insulating core body is a of solid body structure formed by enclosing three side surfaces; the outer sleeve is arranged on the outer part of the insulating core body in a coveringmode; the first connection mechanism is arranged on the end part of the insulating core body and is used for being connected with a wire; the second connection mechanism is arranged on the insulatingcore body and is used for enabling the insulating core body to be connected with an electric pole. According to the composite insulating cross arm, the insulating core body is of the solid body structure formed by enclosing the three side surfaces so that the insulating core body can withstand vertical load, unbalanced longitudinal tension and the like, the ability of a composite insulating crossbar to withstand longitudinal unbalanced tension is improved, the composite insulating cross bar can be applied to a tensile rod, the cross-section utilization rate is improved, the weight of the insulating core body is reduced to the greatest extent, the first connection mechanism and the second connection mechanism enable the insulating core body to be connected with the wire and enable the insulating core body to be relatively fixed to the electric pole, and the stable and safe operation of the composite insulating cross arm is ensured.