Based on the backscattering turbidity measurement method, a turbidity sensor with Y shaped optical fiber bundle probe structure in conjunction with a plane mirror is designed by using the optical fiber sensor technology. Turbidity is estimated in terms of total interaction coefficient, a parameter that contains strong signature of the turbidity of a solution. A scattered light model based on Monte Carlo simulations is applied to estimate the power collected by the fiber optic probe. The turbidity sensor is simple, and it′s useful for detecting suspended impurities even in small quantities within a liquid, the total interaction coefficient of which is as low as 0.059 cm-1. With the reasonable use of the mirror, the sensitivity of the sensor is improved more than 10 times. The proposed sensor can be used for the portable measurements and the on line monitoring can be realized by combining the space division multiplexing technology and time division multiplexing technology.