Abstract: Malachite green (MG) is an important risk affecting the quality and safety of aquatic products, and its stability is affected by many factors. Malachite green is metabolized into leucomalachite green (LMG) after entering aquatic animals. In this paper, in order to investigate the effects of breeds and preservation conditions on the stability of malachite green, these factors were studied in Hypopththalmichthys molitrix and Cyprinus carpio by the liquid chromatography-tandem mass spectrometry (LC/MS/MS) based on LMG recovery. The silver carp and carp samples were operated and preserved in different conditions by adding LMG solution, and the dependences of LMG content on time were studied. The results showed that the matrix breed was the most important factor affecting the results of LMG. Carp matrix frozen for 1-5 months had little effect on the recovery of LMG with the recovery of 90%-110%, while silver carp matrix frozen for 3 months had great influence with the recovery of 30.7%. The storage time of blank matrix and the preservation conditions of matrix after adding LMG standard were another two important factors affecting the recovery of LMG. Fresh silver carp and carp matrix had little effect on the results of LMG. However, the long storage time of blank matrix, and the high preservation temperature and long storage time of matrix after adding LMG standard caused a low recovery of LMG. The time interval from weighing sample to standard addition had not obvious influence on LMG recovery. When carrying out competency verification or quality control in laboratories, fresh carp matrix samples should be a better choice which will be tested as soon as possible. If the sample cannot be detected in time, it needs to be frozen and tested as soon as possible. This study provides references and technical supports for laboratory internal quality control and capacity verification by external adding method.