The invention discloses a guide rail type elliptic oscillating mechanism adjustable in eccentricity. The guide rail type elliptic oscillating mechanism comprises a work plate, a driven shaft, a guide rail sliding block, a groined guide rail, an upper connecting rod, a lower connecting rod, cylindrical sliding blocks, a cross-shaped sliding groove, an upper machine frame, a driving shaft, a motor and a bearing base. When the driving shaft rotates, the cylindrical sliding blocks move along the cross-shaped sliding groove, each point of the upper connecting rod and the lower connecting rod generates an elliptical orbit, the driven shaft drives the work plate to do elliptic motion on the groined guide rail under the driving effect of the upper connecting rod, the position of the driven shaft in an adjusting groove of the upper connecting rod is changed, then the major axis and the minor axis of an ellipse can be changed, and therefore the eccentricity of the elliptic motion can be adjusted. The guide rail type elliptic oscillating mechanism is compact in structure, rigid connection is adopted, and an oscillating system is safe and reliable.