Precise time synchronization is essential for 5G systems, data centers, industrial automation systems, military fields, and more. Although the precision of IEEE 1588 PTP can achieve sub-hundred-nanosecond accuracy, it works only when being deployed hop-by-hop within a LAN with limited range. Hop-by-hop deployment leads to high deployment costs and makes it inapplicable over the Internet. In this paper, we propose the multi-hop precision time protocol (M-PTP), a high-precision and low-cost time synchronization protocol, which does not require hop-by-hop deployment, and no special functions need to be added to the network relay devices such as routers and switches. M-PTP leverages two key ideas. First, to mitigate the "asymmetry in forward delay and reverse delay" problem, SVM-based delay estimation is used to calculate the distribution of positive and negative random delays, then L-estimator is leveraged to estimate the time offset. Second, based on time offset, M-PTP exploits loop effect optimization among nodes. We implemented the protocol and tested its performance on variance hops under different traffic conditions and CPU loads. The experimental results show that M-PTP can achieve a precision of 11.61ns at 5 hops, which is approximately 3 times the precision of HUYGENS and approximately 30 times the precision of PTP.