The invention provides an assembled camshaft for an engine. The assembled camshaft for the engine is of a segmented structure and is composed of two or more shaft segment units, the front ends and therear ends of the shaft segment units are provided with conical surface shafts and conical surface holes correspondingly, the front ends and the rear ends of the shaft segment units are provided withpositioning pin holes and positioning grooves correspondingly, the shaft segment units are provided with center holes, the assembled camshaft is assembled together by sequentially connecting all the shaft segment units in the front-rear direction, each shaft segment unit is coaxial with the former shaft segment unit through conical surface matching, a phase position of a cam on each shaft segmentis positioned through a corresponding positioning pin and the corresponding positioning groove, and all the shaft segment units are connected and fixed through bolts penetrating through the center holes. The assembled camshaft has the advantages that due to the self-centering effect of conical surface matching, the coaxiality of all the shaft segment units after assembly can be guaranteed, machining is more convenient through the segmented structure, all the shaft segment units have certain universality, special equipment and tool are conveniently adopted for large-batch machining to lower thecost, the camshaft is assembled without the special equipment and tool, all the shaft segment units can be replaced separately, and using and maintenance are convenient.