In order to study the relation between the content of inclusion in different pines and the population amount of Monochamus alternates, in the present work, the population density of Monochamus alternatus was anatomically investigated in different forest stands. The results showed that the densities of Monochamus alternatus in P.thunbergii, P. massoniana and P.elliotii were on average 32.63 heads, 16.9 heads and 12.44 heads per plant, respectively. Statistical analysis indicated that the population amount of Monochamus alternatus in P.thunbergii was significantly higher than those in P.massoniana and P.elliotii. In addition, the protein, soluble sugar, water, N, P, K, S, Cl, Ca, Mg, Cu, Zn, Fe, Mn, 16 kinds of free amino acids and 16 kinds of hydrolysis amino acids in branches and phloem were further measured in P. thunbergii, P.elliotii, and the relationships between these above contents and the population density of Monochamus alternatus were also analyzed. The results demonstrated that there was very significant correlation between protein(x1), solublesugar(x2) and the population density of Monochamus alternatus (y), and the correlation formula is y=-44.07-1.5601x1+6.9355x2(R=0.8374*); whilst the correlation formula of free amino acid and population density of Monochamus alternatus is y = 63.24-1.1775x5-0.0680x11+0.1665x12 - 0.1257x15(R=0.9999**), here x5, x11, x12 and x15 denoted as glycine, tyrosine, phenylalanine and prolime, respectively; the correlation formula of hydrolysis amino acids and population density of Monochamus alternatus is y = 37.59 - 0.1146x10 - 0.5741x11 + 0.0112x15 + 0.1468x16(R=0.9955**), here x10, x11, x15 and x16 are defined as tyrosine, proline, arginine and leucine, respectively; and the correlation formula of mineral elements and population density of Monochamus alternatus is y = -67.94 + 409.4696x3 + 37.4746x6 -1004.4480x7 + 4.2958x8(R= 0.9826*), where x3, x6, x7 and x8 are token as K, Ca, Mg and Cu, respectively. Based on these above results, the relationship between the 14 kinds of selected contents and population density of Monochamus alternatus was further analyzed, finding the correlation formula is y = 19.94 + 0.0114x2 + 0.0457x4 - 0.5317x5 + 62.5214x9(R=0.9966**), here x2, x4, x5 and x9 stand for hydrolysis tyrosine, hydrolysis proline, free tyrosine and K, respectively. These above analysis have indicated that the four kinds of factors, i.e. the hydrolysis and free tyrosine, hydrolysis proline and K content, have very significant impact on the population density of Monochamus alternatus.