It ’s not only the trend of world to be telecommunication liberalization and open market, but also the priority to administer the law in the recently years in Taiwan. And the essence of law is creating a reasonable and fair environment, encouraging the fair competition and ensuring consumers’ right. Therefore, the price regulation plays a important role under this trend. "Price-cap" regulation is a incentive regulation to increase efficiency. And it ’s regarded better than "rate-of-return" with cost-plus attribute. The research attempts to assess performance the price cap scheme in the UK, the USA and Australia have resulted in decreasing price in evidence. We conclude that price-cap is suitable for a immature competition market. Further, the empirical assessment of performance has to based on long-run observation with more objective sight.