A digital signal processor(DSP) based position calculation circuit was developed and tested for beta camera. The previous position calculation circuit which employed flash analog to digital(A-D) converters for A-D conversion and ratio calculation occurred significant line artifacts in the image due to the differential non-linearity of the A-D converters. The new position calculation circuit uses four A-D converters for only A-D conversion of the analog signals from the position sensitive photomultiplier tube (PSPMT). The DSP reads the A-D signals and calculates the ratio of Xa / (Xa + Xb) and Ya / (Ya + Yb) in event by event basis. The DSP also magnifies the image to fit the useful field of view(FOV) and rejects the events out of the FOV. The line artifacts in the image was almost eliminated.