In this paper,we have researched the modulation of the upstream channel in optical-cable modem system.The discrete wavelet multitone(DWMT) modulation was compared with other modulations and its characteristics were analyzed.As a main part,we have brought forward a test system model of the DWMT modem and designed a optical-cable modem system.Moreover,we simulated the performance of the DWMT using the computer.The simulation and analysis indicate that the DWMT modulation adapts to the upstream channel in optical-cable modem system.