The unit has assigned security guards to outsourcing companies. Do I need to cancel the contract first?

In principle, it needs to be lifted. The details can be worked out according to the agreement signed by the third party.

Property companies outsource security services. If the outsourcing company signs a labor contract with the security guard and accepts the management of the outsourcing company, it is deemed that the property company terminates the labor relationship with the security guard and needs to pay economic compensation. In practice, if the property management company and the outsourcing company reach an agreement, the outsourcing company will continue to undertake the continuous working years of the security personnel, and the security personnel agree, there is no need to pay economic compensation.