A method for a Precision Time Protocol synchronization network, comprising: Executing, by a slave clock apparatus, an operation of time synchronization with a first apparatus according to Precision Time Protocol, PTP, through a first port, wherein the first apparatus is an upstream node of the slave clock apparatus, the first apparatus is located on a first link, a link from a master clock apparatus to the slave clock apparatus comprises the first link and a second link, the slave clock apparatus comprises the first port and a second port, the first port is located on the first link, the second port is located on the second link, a state of the first port is slave, and a state of the second port is passive; setting the state of the second port to slave; obtaining, by the slave clock apparatus according to the PTP through the second port, information required for determining a time offset between the slave clock apparatus and a second apparatus, wherein the second apparatus is an upstream node of the slave clock apparatus, and the second apparatus is located on the second link; and determining, by the slave clock apparatus, an offset according to the information, wherein the offset is equal to M multiplied by the time offset, and M is not equal to 0; wherein after the determining, by the slave clock apparatus, an offset according to the information, the method further comprises: if an absolute value of the offset is greater than a threshold, determining, by the slave clock apparatus, that time synchronization performance of the first link is faulty or time synchronization performance of the second link is faulty; wherein after the determining, by the slave clock apparatus, that time synchronization performance of the first link is faulty or time synchronization performance of the second link is faulty, the method further comprises: Sending, by the slave clock apparatus, a message to a third apparatus, wherein the message is used for identifying that the time synchronization performance of the first link is faulty or the time synchronization performance of the second link is faulty. Executing, by a slave clock apparatus, an operation of time synchronization with a first apparatus according to Precision Time Protocol, PTP, through a first port, wherein the first apparatus is an upstream node of the slave clock apparatus, the first apparatus is located on a first link, a link from a master clock apparatus to the slave clock apparatus comprises the first link and a second link, the slave clock apparatus comprises the first port and a second port, the first port is located on the first link, the second port is located on the second link, a state of the first port is slave, and a state of the second port is passive; setting the state of the second port to slave; obtaining, by the slave clock apparatus according to the PTP through the second port, information required for determining a time offset between the slave clock apparatus and a second apparatus, wherein the second apparatus is an upstream node of the slave clock apparatus, and the second apparatus is located on the second link; and determining, by the slave clock apparatus, an offset according to the information, wherein the offset is equal to M multiplied by the time offset, and M is not equal to 0; wherein after the determining, by the slave clock apparatus, an offset according to the information, the method further comprises: if an absolute value of the offset is greater than a threshold, determining, by the slave clock apparatus, that time synchronization performance of the first link is faulty or time synchronization performance of the second link is faulty; wherein after the determining, by the slave clock apparatus, that time synchronization performance of the first link is faulty or time synchronization performance of the second link is faulty, the method further comprises: Sending, by the slave clock apparatus, a message to a third apparatus, wherein the message is used for identifying that the time synchronization performance of the first link is faulty or the time synchronization performance of the second link is faulty.