Abstract: This paper investigates the optimal placement of proxies of a web server in the Internet, with the consideration of both read and write operations to the data on the web server. First, we study the problem of optimal placement of k proxies in a system to minimize the total access cost to the web server. Then, for unknown number of proxies, we find the optimal number of proxies required in the system. The problems are formulated by using dynamic programming method and optimal solutions are obtained. Intensive simulations have been conducted to evaluate the performance of the proposed algorithms, and to demonstrate the relationship between the number of proxies required in the system and the read-write ratio. This work can significantly alleviate the web access traffic in the Internet and improve the performance of the web server.