An optical testing system includes: a testing probe, a collecting unit, and a processing unit, wherein the testing probe includes a plurality of spectrum photodiodes used for emitting and casting monochromatic light to a sample, wherein the wavelength of the light emitted by at least one spectrum photodiode is different from that of any other. The collecting unit collects multi-way signal light obtained after the emitted monochromatic light is reflected by the sample surface. The processing unit includes a photoelectric conversion module, an adding module and a testing module. The photoelectric conversion module converts the collected multi-way signal light respectively to multi-way electrical signals. The adding module performs an adding operation for the multi-way electrical signal to obtain an operation result. The testing module tests a quality parameter of the sample according to the operation result, and outputs a testing result.