A method and a system for process upgrade are disclosed. A source process implements data interaction, via a socket interface, with a far end entity connected with the socket interface. When the source process intends to upgrade itself, the source process copies its process data to a target process and determines if the data from the far end entity received via socket interface is complete. If it is determined that the data is complete, the source process ceases data interaction with the socket interface and copies the received data to the target process. After the data is copied, the source process sends an upgrade and switch indication to the target process and enables the target process to send an upgrade and switch request to the socket interface. The socket interface then switches a socket interface service to the target process. Accordingly, the technical solutions according to the present invention realize a reliable and smooth process upgrade without disconnecting the socket connection.