The invention provides an insulating coating liquid for oriented silicon steel of anti-adhesion sheets and a coating process thereof. The coating liquid comprises 100 weight parts of dihydric phosphate, 1.4 to 4 weight parts of soluble molybdate and/or tungstate, 15 to 30 weight parts of chromic anhydride (CrO3), and 50 to 120 weight parts of silica sol or alumina sol. The coating liquid can be used for oriented silicon steel coatings, particularly insulating coatings on magnesium silicate ceramic layers. The insulating coatings can apply proper tension to oriented silicon steel plates, provide insulativity, reduce the adhesion phenomenon under the condition of annealing at the temperature of between 600 and 950 DEG C for 1 to 3 hours, simultaneously maintain the cluster, smoothness and stability of the insulating coatings, and particularly effectively avoid the poor machining of the oriented silicon steel caused by adhesion of the insulating coatings in the iron core winding processing technology.