In order to theoretically reveal the effects of signaltonoise ratio and the required bit error rate level on limit communication rate of a discrete multitone datalink, in this paper, the electrooptical transfer function of the transmitter, the opticalelectro transfer function of the receiver and the total transfer function of generalized visible light communication channel were analyzed. Mathematical modeling of discrete multitonevisible light communication system was finally established by sufficiently considering the time and frequencydomain responses of visible light communication channel. Fomulative relations of limit communication rate versus signaltonoise ratio and bit error rate level were derived. Analytical results show that, under definite signaltonoise ratio, the limit communication rate reveals doubleexponential increasing relation with bit error rate level; under definite bit error rate level, the limit communication rate reveals Boltzmann variation trend versus signaltonoise ratio. With the universal white light emitting diode and PIN detector, when the signaltonoise is 25 dB, the limit communication rate is within the range of 200~228 Mbps for requiring a bit error rate of <10－3, which shows good agreement with the reported experimental results (202~231 Mbps).The novel thereotical analysis method and mathematical modelling proposed in this paper can also be adopted to evaluate the limit communication rate of any discrete multitonevisible light communication system, and therefore they are efficient in system parameter optimization and component selection during the design of such kind of systems.