Reducing or decreasing light scattering effects of suspended particles in water is one of the key technical issues of the direct spectroscopy chemical oxygen demand (COD) water quality detection. Therefore, based on the Mie scattering theory, the improved continued fractions combining with backward recursion algorithm is used to study ultraviolet (UV)- visible light scattering properties on the alga and sand suspended particles in water. The light scattering models of spherical particles in water is built. The changes of light scattering intensity and scattering angle are analyzed and calculated with particle size in the range of 1~200 μm and the incident wavelength in the range of 200~1000 nm. The simulation results show that when the particle size and the wavelength of incident light change, the scattered light intensity and angle are significantly changed with two types of suspended particles. It is helpful to improve resolution and degrade the effect of scattering of detection of water quality using UV-visible absorption spectroscopy.