The invention discloses a voice encryption method after interoffice hard handoff, and the method comprises: after the interoffice hard handoff, a mobile services switching center acquires a private long code mask from a mobile station from a main control mobile switching center of the mobile station, and hands down the private long code mask to a base station, then the base station hands down the private long code mask to the mobile station; and the mobile station implements the voice encryption processing according to the private long code mask. The invention realizes the voice encryption function of the mobile station after the interoffice hard handoff, and is applied to the code division multiple access technique field, and has advantages of simple method and easy implementation.