Filterless color discriminative imaging system is greatly demanded, with the pixel size shrinking to subwavelength. Nanowires have broad applications in photodetectors and have excellent ability to discriminate color by the cavity mode effect due to its well-controlled geometry. Here we use the finite element method to simulate a coned nanowire device which can split the light as well as serve as a photodetector array. The numerical simulation results show that the important parameters such as the wavelength range and resolution realized by the device can be modulated by the top radius, bottom radius, length, and material as well. And we also analyze how the surroundings and the incident angle affect the performance of the device. These results have important reference significance for the practical application of tapered nanowires as photodetectors.