1.A comparative study of the species composition of zoobenthos on diffe- rent substrata in the Northern part of Yellow Sea indicates that there exists a great similarity in the eastern fine sand and very fine sand areas in the nor- them extremely fine sand area,and in the southern extremely fine sand and very fine sand areas;but there is a certain difference in the western fine sand area,the northern extremely fine sand and the southern extremely fine sand and mud-sand areas. 2.The main peculiarities of the total biomass distribution of zoobenthos in the northern part of Yellow Sea are as follows:an uneven distribution of biomasses is found in the coastal waters The biomass off the eastern coast of the Liao-tung Peninsula is higher at the depth of less than 40m.than at the depth of 30 m.or than at the depth 30 m.off the northern coast of the Shangtung Peninsula.The biomass distribution is relatively even in the central region of the northern part of Yellow Sea.The biomass is highest in the south of Dairen and Hai-yang Island,north-east of Chenshantou and off the mouth of Yalu River. 3.As for seasonal variations,the total biomass is highest in the spring, moderate in summer and autumn,and lowest in winter.Seasonal variations of the biomass composition of the four main groups of zoobenthos are as follows: The biomass of the Crustacea is higher in the spring and lower in the summer and winter;that of the Annelida is higher in the summer and lower in the spring,autumn and winter;that of the Mollusca is higher in the winter and very low in the summer;that of the Echinodermata is higher in the spring and autumn,and lower in the winter. 4.The peculiarities of the seasonal distribution of the main species of zoobenthos are as follows:(1)The cold-water species(such as Ophiura sarsii,Oregonia gracilis,Pagurus ochotensis,Crangoo affinis etc.)are absolutily dominant in quantity,and distribute mainly in the region of high salinities and low temperatures,at a depth of more than 50 m.(especially in the region within the sphere of influence of cold water masses).(2)The warm-water species(such as Metapenaeopsis dalei,Palaemon graveri,Yrachypenaeus curvirostris,Ophiura kinsbergi etc.)are less in number,and distribute mainly in the shallow waters of lower salinities and higher temperatures along the eastern cosat of Liao-tung Peninsula and the northern coast of Shangtung Peninsula. 5.Yearly variations of total biomass and biomass composition of zooben- thos in March during the four years(1960～1963)have shown that file total biomass is highest in 1963,next in abundance in 1960 and 1961,and lowest in 1962;and that in the composition of biomass,the annelida and Crustacea are more in 1960～1961 than in 1962～1963,while the Echinodermata has the highest and the Mollusca the lowest biomass in 1963.