Abstract: 【Objective】To observe effects of spraying exogenous ethephon and litchi high yield reagent on litchi flower thinning and to analyze its influence on fruit quality and leaf total N content，so as to provide theoretical reference for scientific and appropriate use of ethephon and litchi high yield reagent in litchi flower thinning and high quality and high yield cultivation.【Method】A single-factor randomized group test design was adopted. Spraying 53 mg/L（T1），106 mg/L（T2），160 mg/L（T3）of ethephon solution and litchi high yield reagent solution（T4）and water（T5）as control on the Guiwei litchi tree crown at initial flowering stage，respectively. The amount of fallen flower branch stalks，flower buds，flowers，and fallen fruits was recorded. And the fruit quality and total N content of leaves were determined. 【Result】The order of the number of fallen buds and flower branch stalks in the 5 treatments was T3>T2>T1>T4>T5，and the order of the number of fallen fruits was T5>T4>T3>T1>T2. No significant effects of the 5 treatments on single panicle fruit weight，fruit number，small diameter，fruit shape index and soluble solid content（P>0.05，the same below） were found. Moreover，no significant difference between the treatment groups and the control was found in pulp texture， flavor，aroma，astringency and brown degree of pulp intine. But spraying exogenous ethephon and litchi high yield reagent could affect the single fruit weight，edible rate and seed weight. The order of single fruit weight was T2>T1>T4> T3>T5，the maximum single fruit weight was 19.45 g，which was 42% increased than the minimum of 13.68 g. In T1， T2，T3 and T4 treatment groups，the edible rate ranged from 78% to 79% which was 30%-32% higher than control；the wilted-seed rate ranged form 97% to 99% which was 31%-34% higher than T5（water treatment group）. The order of total N content of leaves was T2>T1>T4>T3>T5，however，there was not significant difference between the 5 treatment groups and control. The correlation coefficient of single fruit weight，peel weight，seed weight，edible rate，wilted-seed rate，soluble solid substance content and total N content was 0.886，0.851，0.898，0.739，0.740 and -0.947，respectively. The single fruit and seed weight was significantly positive correlated with total N content（P<0.05，the same below），and the soluble solid substance content was significantly negative correlated with total N content.【Conclusion】The application of ethephon and litchi high yield reagent can help Guiwei litchi flower thinning and the ethephon concentration of 106 mg/L has the best effect of controlling flower cluster，therefore，it can be used for litchi production，which is beneficial for saving labor and increasing production.