A downward pressing mesh mechanism and sinker thereof for flat knitting machines in which the downward pressing mesh mechanism includes a needle seat (10) containing a bearing surface (11) to hold a plurality of sinkers (7) and knitting needles (8) separated by spacers (3) and a cam holder (2) localed above the sinkers (7) to hold a cam (20). The cam (20) has a guide track (21) to drive the sinkers (7) swinging. The spacers (3) are vertically run through by a bracing shaft (4) at a lower side. Each sinker (7) includes a yarn pressing portion (75) to press a yarn to form a mesh, a swing guide portion (70) driven by the guide track (21) and a shaft rotating recess (73) to couple with the bracing shaft (4). The sinker (7) thus structured is simpler and durable, hence can be produced and assembled. or repaired and replaced easier and faster. Thus manpower and material costs can be reduced, and product prices also are decreased to meet market requirements.