The heavy oil fields in the Bohai Sea are characterized by low productivity. The heavy oil area of SZ36- 1 Oilfield is chosen for a pilot area which aims at improving both well productivity and ultimate recovery efficiency. Based on the existing inverted nine-spot pattern, five multilateral wells are located in the stably distributed sands with relatively thicker pay zones where put into production along with those existing directional well. It has been proven to be successful with the productivity of a multilateral well as high as 90 to 150 m3/d, which is 3 to 4 times than that of a directional well. Reservoir numerical simulation result shows that the increment of the ultimate recovery efficiency in pilot area could reach as much as 4%. The successful drilling and developing ofmultilateral wells breaks a new path to efficiently develop heavy oil fields.