The performance of electron beam is firmly associated with shape for electron beam stream which reflects its focus state. With contour map algorithm various power distribution regions were segmented by multi-level power density value sets. Based on iterating policy the power density value was computed by specialized power region value. The theory was analyzed and algorithm steps were depicted in detail. 2D regular grid logical interpolation states with isovalue were explained and four cases for contour propagation were concluded particularly. A criterion for selecting candidate isovalue points was analyzed. An illustration for contour propagation denotes tracing process for isovalue points of different grid units which forms contour map. A contour map plotting of multi-value power regions appearance was achieved with parameters for various shapes. Experimental results on various datasets demonstrate the effectiveness and robustness of our method.