A path calculation method, apparatus, and device, to implement network slicing. The path calculation method includes: obtaining an algorithm constraint supported by each of a plurality of network devices, where the algorithm constraint is a constraint of a forwarding path algorithm, and the forwarding path algorithm is used to calculate, for the network device, a forwarding path that meets the algorithm constraint; performing network topology division on the plurality of network devices, where network devices in a same network topology support a same algorithm constraint; and calculating a forwarding path between network devices in each network topology based on the algorithm constraint, of the forwarding path algorithm, corresponding to the network topology.