Abstract: The existing condition assessment methods of mine-used transformer mostly focus on assessment model and theory research, while neglect temporal and spatial correlation analysis of evaluation indexes. In view of the problem, an insulation condition assessment method of mine-used transformer based on spatio-temporal information fusion was proposed. In view of randomness and fuzziness of data information in the insulation condition assessment method of mine-used transformer, a multilateral condition assessment system of mine-used transformer was established. Variable weight coefficients of factors layer of evaluation model were determined introducing association rules and variable weight synthesizing theory. A fuzzy membership function was formulated to describe the factor layer, and its original basic probability assignment was calculated. The basic probability assignment of factors and cycles in evaluation model was fused based on D-S evidence theory, firstly, basic probability assignment of factors obtained by the assessment factors layer and its weight coefficient were fused based on time domain information fusion, and then the time domain fusion information was used for airspace fusion, finally insulation condition of mine-used transformers was judged combining reliability criterion. The results of practical example prove that the proposed method can evaluate the insulation condition of mine-used transformers accurately and effectively.