A method for operating PON (passive optical network) user terminal and a PON user terminal equipment, when there is only few data service request in the PON, the PON user terminal operates in power saving manner which maintains low speed connection, the method comprises: a judgment condition that the PON user terminal changes to power saving state is set; the PON user terminal determines whether its own state meet the judgment condition changing to power saving state, if so, it transmits a request to change to power saving state to the OLT (optical line terminal); after the PON user terminal receives the respond that the OLT has accepted the request, it controls parts of the modules therein to change to power saving state, and intermittently switch over between power saving state and normal state. The invention allows saving power under the condition that keeps the low speed service uninterrupted, in the meanwhile alleviates the pressure of ONU terminal thermal design.