The purpose of this paper is to study the “threshold effect” between the proportion of mutual fund’s holding on electronic company and its stock prices by applying the panel threshold auto-co-relation model. It examines if there is one or multiple optimal thresholds to have reverse effects between the proportions of the stock holding and the stock prices. Applying the empirical results, we can conclude that investors can increase their stock holding when the proportion of the mutual fund’s holding starts increasing from a very low level. Even the stock prices fall in the beginning when the proportion of the mutual fund’s start increasing in a falling market. However, the stock prices eventually go up higher from a long-term perspective. On the other hand, it is less indicative that the stock prices go up or down when the market is consolidating according to the empirical results. Finally, the transaction volume is positively related to the stock prices and therefore is a useful indicator. On the other hand, the Nasdaq index or the exchange rate is less useful.