The invention discloses a privacy protection method during data aggregation of a wireless sensor network. Privacy protection in a data addition aggregation process and a multiplication aggregation process is realized on the basis of an elliptical curve algorithm. The privacy protection method comprises the following steps of: determining, by a target node, an elliptical curve parameter and a private key k, calculating a public key K and broadcasting the elliptical curve parameter and the public key K; encrypting, by each source node, a plain text by an elliptical curve algorithm by using a random number, the elliptical curve parameter and the public key K and transmitting a cipher text message; performing, by a middle node, aggregation operation on the received cipher text message and transmitting an aggregation result to the target node; and decrypting, by the target node, the received aggregated cipher text data by using the private key k according to the elliptical curve algorithm to obtain aggregated plain text data. Compared with the prior art, an elliptical curve encryption technology adopted in the invention has the advantages of small public key digit, high calculation speed and the like, and two aggregation operation modes of addition aggregation and multiplication aggregation can be realized.