The structural parameters and related experimental studies of a tunable all-solid-state external-cavity frequency-doubled CW 671 nm ring laser are described in this paper.The “8” ring external-cavity frequency-doubled resonant is adopted,the external resonant cavity is locked based on the PDH(Pound-Drever-Hall)frequency locking technology,and the external-cavity frequency-doubled output is realized.In the experiment we obtain 650mW CW tunable 671nm red light output with 50.6 % light conversion efficiency,by using a tunable 1342nm continuous light as the input source at 1.3 W.