The embodiment of the invention discloses a carrier-grade address translation device and a customer address mapping relation processing method thereof. The customer address mapping relation processing method comprises the steps of configuring parameters of a customer address pool, an IPv4 public address pool, a port block size and a port range; calculating a customer address sum N, an IPv4 public address sum m and a usable port block sum n according to the configured parameters; for k*m+1 to (k+1)*m customer addresses of N customer addresses, sequentially allocating IPv4 public addresses and port blocks corresponding to each line of elements (such as public addresses and port blocks) in the (k+1)th column in an m*n matrix consisting of m IPv4 public addresses and n usable port blocks, and creating a customer address mapping relation; and querying the customer address mapping relation according to the customer addresses in a customer message, and obtaining an IPv4 public address and a port block corresponding to the customer address, and hereby, performing carrier-grade address translation process on the customer message. According to the embodiment of the invention, the opportunities that the customer address mapping relation is found out by illegal customers can be reduced, and the influence of malicious port occupancy on application access of legal customers is avoided.