The life limitation of an electrochromic cell using tungsten oxide films and a non-aqueous lithium liquid electrolyte, together with the reason for its degradation were investigated. The degradation phenomenon has been summarized in observing that the resistance of a cell became higher and injection charge decreased as the number of switching cycles increased. Namely, the coloring charge efficiency became lower, and, under the same operating condition, the contrast became poor. The origin of the mechanism dominating the degradation is essentially in the accumulation of lithium in the film, which results in decreasing both the amount of charge injecting into the film and the coloring charge efficiency. The authors tried to improve the life characteristics, especially by regenerating the accumulated lithium in the tungsten oxide film and were convinced that this is one of the way to improve switching life. However, estimating from overall observations, the life limitation was approxi-mately 1×107 switching times.