The invention provides a method for lightweight security synchronization in a smart sensor network. The method comprises the following steps of step S1 an authentication stage, namely broadcasting an authentication message between a sensor node and an application program; step 2 a timestamp transfer stage, namely transferring timestamp information through a lightweight encryption algorithm to guarantee communication security; and step S3 a time synchronization stage, namely considering pulse propagation time delay of the authentication stage and the timestamp transfer stage to carry out time synchronization adjustment. The method can be applied to ISO (International Standardization Organization)/IEC (International Electrotechnical Commission)/IEEE (Institute of Electrical and Electronic Engineers) 21451; security needs in a synchronization mechanism are fully met, the security is improved, and some false and invalid information can be discarded in a transmission process; the security performance of time synchronization is only improved at the cost of fine delay, and meanwhile, the method can be applied to a sensor network of ISO/IEC/IEEE 21451.