A laser-diode (LD) side-pumped Nd∶YAP all-solid-state intracavity frequency-tripled 447 nm continuous-wave (CW) blue laser was reported. After analysis and comparison of several optical crystals, Nd∶YAP was chosen as the gain medium to generate 1341.4 nm fundamental laser. Inside the cavity, a type Ⅰ critical phase matching (CPM) LBO crystal was used for 670.7 nm second harmonic generation (SHG), and a type Ⅱ CPM KTP was used for sum frequency mixing (SFM) of the 1341.4 nm and 670.7 nm radiation to generate 447.1 nm blue light. By using a four-mirror folded-cavity resonator, the parameters of laser cavity were optimized and selected according to cavity stability analysis. Output characteristics of different cavity lengths were studied by experiment. The output power of 447.1 nm CW blue laser reached 114 mW at the incident pump power of 534 W, corresponding to an optical-to-optical conversion efficiency of 0.02%, and the causes of low efficiency were analyzed.