Micro and nano wavelength beam splitter is an important beam-splitting device in photonic chips. In this study, the Sequence Quadratic Program (SQP) is involved to design ultra-compact wavelength beam splitters with footprints of 1.5μm×1.5μm. The Y-type dual channel beam splitter can realize TE/TM mode splitting at the same time, the transmissions of TE mode light at 1140nm and 1200nm are 80% and 81%, and the extinction ratios are 18.1dB and 16.3dB, respectively; The transmissions of TM mode light are 70% and 67%, and the extinction ratios are 18.3dB and 15.9dB, respectively. The T-type beam splitter has realized 180-degree separation angle splitting, and the transmissions of optical power at the wavelengths of 1100nm and 1170nm have reached 88% both, and the extinction ratios are 16.6dB and 15.0dB, respectively. It is the smallest size chip-integrated wavelength beam splitter. The cross-type three-channel beam splitter has realized splitting with a wavelength interval of 50nm. The transmissions at the wavelengths of 1100nm, 1150nm, and 1200nm are 73%, 66%, and 70%, and the extinction ratios are 17.2dB, 13.8dB, and 13.8dB, respectively; The asymmetric three-channel beam splitter has realized splitting with the wavelength interval of 20nm. The transmissions at the wavelengths of 1200nm, 1220nm, and 1240nm are 61%, 56%, and 57%, and the extinction ratios are 10.8dB, 7.9dB, and 8.9dB, respectively. This method has the advantages of a short design period, high design efficiency, simple structure, easy processing, and suitability for designing chip-integrated photonic components. It is expected that it can provide a new idea and a robust method for designing chip-integrated photonic devices.