Taking the disc cams with translating roller follower study object,the organization form,basic /general dimension,accurate description and basic steps for dimension synthesis are given,the coordinate system O- rr,0, e and area dimension space Ω（ r,0,r,e） of dimension are constructed,then discretizeing and gridding of the dimension area is carried out. The four constraint conditions and analytical expressions are put forward,through single or merge visualization- oriented mapping with ergodic method,the corresponding boundary and solution domain are given. Then,according to the multi objective planning and visualization- oriented mapping,it shows some important rules such as carinal dot P,iek,*/ crest line lek/ crest plane Sback and the bottom dot P,ek,**/ valley dot P***,it also reveals the existence of optimal solution. All the consequences are instructive to the dimension synthesis of the mechanism.