The present disclosure provides method and system to facilitate definition, tuning and visualization of a geo-fence at a computer system. The method comprises: receiving input parameters for a geo-fence, the input parameters including one or more parameters specifying a geographical region; sampling historical mobile signals based on one or more of the input parameters; dividing the geographical region into a plurality of areas; determining a weight for each respective area of the plurality of areas based at least on density of sampled mobile signals associated with geographical locations in the respective area; selecting a subset of the plurality of areas based on respective weights of the plurality of areas; and forming the geo-fence using the subset of the plurality of areas, the geo-fence including one or more contiguously closed regions each formed by a cluster of adjacent areas among the subset of the plurality of areas.