The noise of a hybrid soliton pulse source (HSPS) with a linearly chirped fiber Bragg grating is analyzed by couple-mode equations, including spontaneous emission noise when the HSPS is mode-locked. The relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is shown that the noise peak in the RIN spectrum locates at the inverse of the round-trip time in the compound cavity and this peak is a little broad. In this range, a high noise level affects the operation of device, and therefore transform-limited pulses are not obtainable. It is also shown that in the mode-locking range, except approximately at the frequency of the compound cavity, the RIN value is low.