The invention relates to a growth process for silicon nitride in a silicon oxide nitride oxide silicon (SONOS) structure. The growth process comprises the following steps of: a, providing a wafer, and putting the wafer into a low pressure chemical vapor deposition (LPCVD) furnace pipe; b, introducing reactant gas SiCl2H2 and NH3 into the LPCVD furnace pipe to grow an initial membrane layer on thewafer; c, introducing the reactant gas such as SiCl2H2 and NH3 into the LPCVD furnace pipe in a volume ratio of 1:10, and growing an intermediate membrane layer on the initial membrane layer of the wafer; d, while keeping that the volume ratio of the SiCl2H2 to the NH3 in the LPCVD furnace pipe is 1:10, growing a top membrane layer on the intermediate membrane layer of the wafer; and e, continuing to introduce the NH3 into the LPCVD furnace pipe, and stopping introducing the SiCl2H2, so that the SiCl2H2 in the LPCVD furnace pipe reacts fully to form the required silicon nitride layer on the wafer. In the growth process, a process for manufacturing conventional devices is compatible with a metal oxide semiconductor (MOS) process; the process is simple, once the flow of the DCS and the NH3 is set, and the growth time is set, the grown silicon nitride layer is stable and controllable; and thus, the process can be used for preparing the silicon nitride layer with the SONOS structure.