An all solid-state continuous-wave cyan laser at 500.8 nm is presented. By using a new resonator for doubly resonant, two Nd∶YAG are pumped by two laser diode arrays (LDA) coupled by optical fibers, respectively. In the two cavities, wavelengths of 1064 nm from one Nd∶YAG and 946 nm from the other are chosen to be mixed into 500.8-nm cyan laser. Through proper design of the cavity, the optimum matching of modes and gains for the two wavelengths can be obtained. In the overlapping of the cavities, sum-frequency mixing is generated with a type I critical phase matching LBO crystal. The cyan laser output of 223 mW at 500.8 nm with TEM00 mode is obtained at the incident pump power of 12 W for one Nd∶YAG crystal and 8 W for the other. The beam quality M2 value is about 1.2 in both horizontal and vertical directions at the maximum output power. The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high power 500.8-nm cyan laser.