A method and an apparatus for controlling packet transmission and a network functions virtualization (NFV) system, where the method includes determining, by a control device, at least two target service processing units and at least one associated service processing unit, where packets of a target service need to be transmitted to the at least two target service processing units through the at least one associated service processing unit, a first target service processing unit in the at least two target service processing units is configured to perform, on packets of the target service, service processing corresponding to a first software version, and a second target service processing unit in the at least two target service processing units is configured to perform, on packets of the target service, service processing corresponding to a second software version; and sending first control information according to a preset first threshold.