Slow Slide Servo, in comparison with Fast Slide Servo, is a novel machining process capable of generating freeform optical surfaces or rotationally non-symmetric surfaces at high level of accuracy. It is processed in the polar and cylinder coordinates with the method of C, X and X axes. Micro-optical devices, e.g., micro lenses, micro mirrors, play an important role in high speed data, voice and video signal transmissions. Micro array lens can be treated as a freeform surface and therefore can be machined by slow tool servo method. In the tool radius compensation, the discontinuity of normal direction may cause the lathe motion beyond servo axis' capability. In the current research, servo axes limitation motion capability was analyzed and two tool radius compensation methods were studied. Experiments show that by correctly selecting tool radius compensation method, slow tool servo can manufacture array lens in a single operation and accurate geometry and optical surface finish can be obtain.