A method of cleaning an automatic biochemical analyzer, wherein the cleaning solution includes: at least one anionic surfactant, at least one nonionic surfactant, an alkali metal hydroxide, an alkali metal citrate, and a buffering agent stabilizing the pH value above 13.0. In some embodiments, the cleaning solution provides low residual rate of proteins, low residual rate of lipids, desirable within-batch repeatability in clinical testing, low level of cross-contamination, and low level of reactant deposit after cleaning, without affecting test results of the biochemical analyzer. In some embodiments, the cleaning solution has no corrosive effects on the liquid path and reaction cup of the analyzer. The ingredients of the cleaning solution may also be biodegradable.