A method, apparatus and system for transmitting Ethernet signals in an OTN are provided. The method may include: mapping the Ethernet signals to timeslot units, where a VCG composed of multiple OPUs is divided into the timeslot units; mapping the Ethernet signals into the OPUs, and then mapped into OTUs and output to the OTN for transmitting. In this way, the Ethernet signals may be transmitted in the OTN transparently. The apparatus may further include: a first adaptation protocol frame mapping module, a first virtual concatenation module, and a first line terminal module, which convert the Ethernet signals to the OTUs. The system may include a first adaptation protocol frame mapping module, a second adaptation protocol frame mapping module, a first virtual concatenation module, a second virtual concatenation module, a first line terminal module, and a second line terminal module, which convert the Ethernet signals to the OTUs and vice versa.