The utility model relates to the technical field of drill wellhead devices, in particular to a heavy oil observation well casing head, which comprises a hanger, a casing, an auxiliary pipe, a body and an oil pipe short joint, wherein a ring-shaped boss is arranged on the outer wall of the middle portion of the hanger, the outer wall of the lower portion of hanger and the inner wall of the upper portion of the casing are fixedly arranged together, a step hole with a big upper portion and a small lower portion is arranged on the ring-shaped boss in the axial direction, the upper portion of the auxiliary pipe is sleeved in the step hole, the auxiliary pipe which is arranged below the ring-shaped boss and the casing are fixedly arranged together, an upper pressing plate, an auxiliary pipe sealing part and a lower pressing plate are orderly arranged in the step hole which is arranged on the upper portion of the outer side of the auxiliary pipe from top to bottom, a hanging boss is arranged on the inner wall of the body, and the ring-shaped boss is seated on the hanging boss. The heavy oil observation well casing head is reasonable and compact in structure and convenient to use, can monitor the situations of steam injection of heavy oil and oil driving and the like in real time, and is safe and reliable to operate, thereby being capable of reasonably arranging mining life, and effectively achieving reasonable and economic mining.