The relationship between investment and shares is established to find the intrinsic nature. It is found when the best labour is 6 the cost is low and the number of shares are 1000 with the intersection of 1~4 RMB which is net profit point. When the best capital is 6 units the profit will be 5 RMB and the profit point is 1400 of the number of shares with the 5 RMB. The profit may become the positive at 780 pieces when the best labor is one. It explains that beyond this point the total net profit may be 3~4 Yuan may be best net profit in average profit. TR£2TC that says the Tpro may be best start because TCquan£0 in intersection between Tpro and TC. The total profit will be 3~4 Yuan according to the best labor and capital. The best labor is 1 whilst the best capital is 6 in this condition. In total TR³2TC is the valid value to make more profit which is concluded in this paper.