The beams of each emitter in the diode laser array are overlapped by spectral beam combination. Each emitter is locked at different wavelengths. Frequency conversion of the combined beam is conducted. When the beams from each emitter satisfy the nonlinear frequency conversion conditions, sum frequency generation of blue light can be obtained. The spectral combined diode laser array can increase the number of lasers participating in the nonlinear frequency conversion, and enhance the whole output power. In the experiment, a standard diode laser array is used. The output power of the spectral combined array is 18.2 W. The output power of the blue light is 93 mW, and the optical-optical conversion efficiency is about 0.51%. The feasibility of the multispectral frequency conversion of the spectral combined diode laser array is proved by the experiment.