Discrete Multitone Modulatin (DMT) has been widely chosen for Asymmetric Digital Subscriber Lines (ADSL). This Paper analyzes the effect of chipping in DMT-based transceivers and compute the chipping noise and the quantization noise produced by the D/A convertor. Compared with the no-chipping, the number of bits for D/A converter is reduced without the loss of SNR. This paper analyses a method to reduce the chipping noise and show that by this method we can get the same result under the not-optimum chipping as that under the optimum chipping.