the evaluation of portfolio performance has always been an important research topic in the fund industry. Performance attribution is to compare the actual performance of fund portfolio with the return of market benchmark, and at the same time, decompose the difference between them (that is, excess return), so as to evaluate the performance of fund managers at different levels (that is, the source of performance). Through the reasonable decomposition of the performance of fund portfolio, it can provide the basis for internal investment research to support and evaluate the performance afterwards, and help to understand whether the realized income is consistent with the expected income, whether the risks assumed match the nature of the portfolio and whether the risks are compensated accordingly, thus helping fund managers to improve their investment performance. Therefore, it is of great practical and theoretical significance to decompose the performance of fund portfolio. In this paper, the evaluation of portfolio performance has always been an important research topic in fund industry. Performance attribution is to compare the actual performance of fund portfolio with the return of market benchmark, and at the same time, decompose the difference between them (that is, excess return), so as to evaluate the performance of fund managers at different levels (that is, the source of performance). Through the reasonable decomposition of the performance of fund portfolio, it can provide the basis for internal investment research to support and evaluate the performance afterwards, and help to understand whether the realized income is consistent with the expected income, whether the risks assumed match the nature of the portfolio and whether the risks are compensated accordingly, thus helping fund managers to improve their investment performance. Therefore, it is of great practical and theoretical significance to decompose the performance of fund portfolio. This paper will make attribution analysis and diagnostic analysis on the investment performance of the funds under E Fund, and make an in-depth analysis on the excess returns and their sources of the funds under E Fund, so as to evaluate the management ability of the fund investment team, and sum up the overall advantages and disadvantages of the fund operation under E Fund. The first chapter of this paper summarizes the related research on performance evaluation; The second chapter briefly introduces E Fund Company and its funds, and introduces Morningstar Company's portfolio performance evaluation of E Fund. The third chapter uses the external evaluation method: Treynor-Mazuy(TM) model to analyze the performance of E Fund in 27-28. The fourth chapter uses the internal evaluation method: Brinson model to analyze the performance of E Fund from 25 to 28; The third and fourth chapters evaluate and analyze the performance management ability and its sources of the fund portfolio from different analysis angles, and finally make a summary and put forward suggestions for improving the investment operation of E Fund.