An all-fiber continuous variable quantum key distribution by implementing discrete-modulated coherent state protocol based on multi-bits coding of single pulse is realized. The system employs a scheme combining polarization and frequency multiplexing. The pulse width of quasi-continuous wave is 200 ns. Each pulse is divided into four equal parts in time domain. In order to increase the secure key rate, the two quadrature components of each part are encoded with random number. At a repetition rate of 1MHz, the system achieves a final secure key rate of 32.8kb/s over a distance of 25km of optical fiber.