The dynamic random optical field, which is formed after the laser is scattered by biology tissues, can be regarded as the superposition of two segmental optical fields. For example, the scattering of skin tissues can either be composed of the scattering of epidermis tissues and erythrocytes in endermic capillary, or be composed of the scattering of erythrocytes in artery and the tissues around them. This paper describe how the different proportions of the two segmental optical fields affect the statistic properties of the composed field.