A wireless optical transmission system is designed and built. According to the system receiver stability and signal-to-noise (SNR) requirements, the photodiode characteristics, circuit stability and bandwidth, receiver noise and signal-to-noise ratio of the receiver are deduced and analyzed in detail. The noise source in the receiver is analyzed in detail and the influencing factors and calculation methods are given. The quantitative calculation is performed according to the parameters of the experimental components. The photodiode preamplifier circuit is modeled and simulated on LTspice-IV. Its signal gain and noise characteristics are analyzed. The results are close to those of theoretical analysis. A 1 MHz square wave transmission experiment is made on the system. Good square wave signals can be obtained at the receiving end. This result shows that it can provide stable and reliable pre-stage signals for the subsequent signal processing module.