The invention discloses a preparation method of a concentrated culture solution of nitzschia closterium minutissima allen et nelson and a plastic barrel cultural mode. The conventional preparation method of the culture solution is immediate preparation; the culture solution is prepared once for use at one time according to the use level, so that the conventional method is time-, work- and labor-consuming, troublesome to weigh and great in error. According to the invention, the concentrated liquor is adopted by the inventor for use for many times, so that the culture solution is simple to operate, convenient to store and convey, suitable for scaled, industrialized, commercialized and professional production, and very convenient. The inventor optimizes the conventional formula and supplements NaHCO3, 920 plant growth stimulin, human urine, sea mud extracting liquor, cow dung and sheep manure lixivia and the like, so that the culture solution is more complete, balanced and abundant in nutrition. As for the cultural mode, the inventor adopts a household mineral water barrel cultural mode to replace conventional open cement pit culture, so that the cultural method is easy to operate, difficult to be polluted, easy to master, agile and diverse, difficult to scratch, safe and reliable, good in transmission of light, low in cost and fast in growth, and the output is improved by 150%.