The present disclosure is related to an integrity protection method and device. In the method, a first BEARER parameter value is obtained based on at least one of the following: a LCID corresponding to data transmitted in the sidelink communication, an access communication standard adopted by the sidelink communication, a BEARER parameter value allocated for the sidelink communication, or a preset BEARER parameter value. A bit length of the LCID corresponding to the transmitted data is greater than a bit length of the first BEARER parameter value. Based on the first BEARER parameter value, a MAC-I or an XMAC-I for the sidelink communication is calculated.