The aim of this paper is to propose a mathematical model for investigating the effective factors on inter and intera organization cooperation amongst related firms in transit of Iran.This model is composed of eight stage conceptual variables such as cost, time, physical distance, route capacity, training, cooperation of related firmsin transit, marketing and rules. Therefore, a population of 70 members is studied and 58 persons helped in collecting data. The required data are collected using interviews and filling questionnaires with 89% reliability. Then, the regression model is obtained using data gathered from questionnaires and interviews with alfa Cronbach and correlation statistical tests via SPSS software. The results show statistically significant relationship between the 8 independent variables and dependent variables (related firms in transit). Meanwhile, the effectiveness of variables physical distance, route capacity and rules not verified. A comprehensive discussion is followed by the results to clarify different aspects of the study. Also, some future study points are stated.