Abstract: In cold areas, the outer PE layer of precast directly-buried insulating pipe may crack during storage and construction process. This paper analyzes the cracking reasons of this HDPE in projects from different aspects, such as physical property, raw materials and formulations of outer pipe, forming processes like extrusion temperature, cooling speed, pulling speed etc., precast process of PE insulation layer, structure characteristics of insulating bending pipe, environmental temperature, and installation process, etc.. This paper gives the repair measures in field repair to cracked insulating pipe with viscoelastic tapes and hot shrink tapes, puts forward relative suggestions in selecting appropriate raw materials, controlling process parameters during the production process, controlling the feeding volume of PE foam, and enhancing the protection of HDPE outer layer, etc..