A downward pressing mesh mechanism and sinker thereof for flat knitting machines in which the downward pressing mesh mechanism includes a needle seat containing a bearing surface to hold a plurality of sinkers and knitting needles separated by spacers and a cam holder located above the sinkers to hold a cam. The cam has a guide track to drive the sinkers swinging. The spacers are vertically run through by a bracing shaft at a lower side. Each sinker includes a yarn pressing portion to press a yarn to form a mesh, a swing guide portion driven by the guide track and a shaft rotating recess to couple with the bracing shaft. The sinker 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.