【摘要】 本文所讨论的积图是图的笛卡尔积G1×G2，目的张量积G1∧AG；，图的逻辑积G2G1和图的强直积G1·G2四种积图。证明了：（1）如果G1和G2都是连通图，则积图中笛卡尔积，逻辑积和强直积都是道路正图。（2）图的张量积G1∧G2是道路正图的是图G1和G2是一个连通图，G1或G2有一个奇圈，且其中λ1和λn分别是图G1的最大和最小特征值，μ1和μm分别是图G2的最大和最小特征值。更多还原

【Abstract】 The Products of Graphs discussed in this paper are the following four Kinds:the cartesian product G1×G2 of graphs,the tensor product G1∧G2 of graphs,the lexicographic product G1G2 of graphs and the strong direct product G1·G2 of graphs. It is proved that: (1)The cartesian product,the lexicographic product and the strong direct product in the products of connected graphs, are the path-positive graphs.(2)If the tensor product of connected graphs G1 and G2 is a pathupositive graph if and only if G1 or G2 has an odd cycle, and max {A1μ1, λnμm}≥2.更多还原