In this article,it is deduced that the simplified one rank differential equation is obeyed by some coagulations of the homologous chain hydrocarbon.The integral formula with three parameters is proved by totally 28-groups literatures regarding the critical temperature of the linear chain alkane and the linear chain alkene.It is very important that the biggest forecast remnant error is 0.72 K and less than measurement errors,so that,the illation algorithm is accurate,and also it is feasible to calculate the cri...