Portable photometer capable of adjusting ultra-long absorption optical path and measuring method thereof

The disclosure provides a portable photometer capable of adjusting an ultra-long absorption optical path and a measuring method thereof. The portable photometer comprises an excitation light source, acolorimetric pool, reflecting mirrors, an auxiliary reflecting mirror and a light collector. The excitation light source is arranged at one end of the colorimetric pool and the light collector is arranged at the other end of the colorimetric pool; and the reflecting mirrors are arranged at the two sides of a colorimetric pool area between the two ends, so that parallel monochromatic light emittedby the excitation light source is reflected and propagated in the extending direction of the colorimetric pool. The colorimetric pool is arranged in parallel with a fixing piece; the fixing piece isused for fixing a smart phone; the arrangement position of the light collector corresponds to a light sensor of the smart phone, so that final transmission light can reach the light sensor through thelight collector. The auxiliary reflecting mirror is arranged at the tail end of the colorimetric pool and, together with the light collector, can guide and collect a light beam deviating in 2N reflection direction to the light sensor. Therefore, the detection sensitivity and accuracy of photometric analysis can be improved and the portability of the device is not obviously reduced.