中文摘要：

利用矩阵运算及算子的基本理论,讨论了由微分算式L_1=D（（2））＋q_1（t）和L_2=D（（4））＋q_2（t）其中（D=d/dx,t∈I=[a,b]）生成的两个微分算子L_i（i=1,2）积L_1L_2的自伴性问题,并在常型情形下,获得了积算子自伴的充分必要条件.

英文摘要：

The self-adjointness of product of operator generated by two different differential expressions is investigated with the theory of operators and matrix operations.And we obtain the sufficient and necessary conditions of product operator which is self-adjoint when differential operators are non-singular.