Abstract: The MCP-PMT’s linear output was always described by the linear current which depends on the input pulse shape. A new parameter called linear output charge which doesn’t depend on the input pulse shape was measured by waveform comparison method. Two types of laser pulses with FWHM of 20 ns and 10 ns, respectively, were used in the experiment. The linear output charge of MCP-PMT was obtained when its gain decreases by 10%, and both results are consistent.