The depositional period of the Maozhuang Formation of the early period of the Series 3 of the Cambrian in North- China Platform was distributed in two facies zones around the oldland, i.e. the restricted tidal- flat facies zone near the oldland and the open tidal- flat facies zone off the oladland. The restricted tidal- flat facies zone is marked by the transgressive purple and red mudstone of the arid red bed (or sebkha facies) and the high- stand dolostone of the clear tidal- flat facies. The open tidal- flat facies zone is characterized the transgressive purple sandy mudstone of the tidal- flat facies and the high- stand limestone of the subtidal facies. The Maozhuang Formation at the Jinzhouwan section in the Dalian City of Liaoning province is composed of an open tidal- flat facies, the high- stand limestone which is marked by a set of bioherm limestones of both the stromatolite and the leiolite interbedded oolitic grainstones, which make up a particular bioherm complex. Several features of this particular complex of bioherm indicate that it is a rare and typical example of microbial carbonates dominated by the cyanobacterial mat: ①In the first unit of the complex of bioherm madding up of large column and domelike silty and muddy stromatolites, the bacinellid fabric indicates that these stromatolites resulted from the calcification of cyanobacterial mats; ②Within the second unit composed of leolites, few sheath fossils of filament cyanobacteria indicate that the formation of leolites is genetically related to the calcification of the relatively thick cyanobacterial mat; ③In the top unit composed of small column like stromatolites, both the sheath fossils of filament cyanobacteria within the stromatolitic columns and the micritic clump composed of cyanobacteria clearly show that these stromatolites were constructed by the microbial mat dominated by cyanobacteria; ④In the third unit, sheath fossils of filament cyanobacteria developed in margin of a ooid indicate that the origin of these ooids is genetically related to the cyanobacterial biofilm. Therefore, this bioherm complex in the upper part of the Maozhuang Formation represents an impressive sedimentological phenomenon and is a typical example for studying the first episode of the cyanobacterial calcification event in the early period of the Phanerozoic Eon.