Free space optical communication (FSOC) technology has been developed rapidly and practically applied in many scenarios such as satellite-related ones, in unmanned aerial vehicles, for underwater use, etc. In certain applications, it is very important to obtain the high-precision position and distance information. The laser ranging technology is one of the main ways to realize it. Moreover, it would be more interesting to accomplish the laser ranging integrated with the FSOC, which can effectively control the size, weight, and power of the FSOC terminals. However, in existing integrated laser communication and ranging solutions, the ranging accuracy is in the millimeter-level. To further improve the accuracy of laser ranging and communication rate in the integrated architecture, we propose a harmonic phase ranging method combined with delta-sigma modulation (DSM) based on a 10 Gb/s coherent FSOC. Through the DSM technology, a harmonic is converted into a digital signal which can be simply combined with the communication data and transmitted together in the FSO link. The laser ranging can thus be effectively combined with FSOC to realize an integrated architecture. Finally, the root means square error of the laser ranging are improved to ∼0.303 mm. Compared with the existing solutions, our proposed scheme shows both advantages of higher-precision ranging and higher communication rate.