Abstract
According to individual variance and covariance formula of traditional formula, linear model and the CAPM, this paper aims to provide a comprehensive analysis of the various components of the investment risk and return rate about their effects on the performance of the stock portfolio. Similarly, relevant variables in the model in order to accurately and prove investment factor caused by the combination of the change of the benefits and risks, this paper will collect TELSA motors and NIO to auto stock data from the Dow Jones stock market (USA) in nearly a year, which could explore the portfolio relationship between the two listed companies and can be able to identify the factors that influence the investment decision. The analysis includes several aspects: the direct influence of accidental risk quantity on variance; the relationship between the amount of unexpected risk M and the rate of stock return; the causes of the overall investment risk; the portfolio benefits and strategy changes represented by coordinate parameter points in CAPM model under different correlated risk variances; the relationship between the portfolio strategy of the two listed companies, the proportion of capital investment and the prediction of the fluctuation tendency between risk and return. The results show that the variation factor of risk return might significantly determine the degree of risk aversion and return of investment while the extreme investment might not be suitable for the portfolio allocation of two companies.