As to the fuel injection system of electronic unit pump, of which fuel supply principles mainly be influenced by fuel supply camshaft. Due to the requirements of the diesel engine for the fuel supply system, a new method is presented to design the constant pressure injection fuel supply cam profile. First, design principles of the fuel supply camshaft profile according to the diesel engine combustion requirement are proposed and then the parametric equation for the camshaft profile can be obtained by the proposed principles which are analyzed through math method. At last, after the prediction and comparison of the designed camshaft profile, the conclusion shows that the fuel injection system designed by the proposed principle can satisfy the injection requirements of the diesel engine. Meanwhile, the parametric equations simplify the design process of camshaft profile so as to improve the reliability and the injection performance of the fuel supply system. (C) 2017 Elsevier Ltd. All rights reserved.