Mobile phone RTK is vulnerable to interferences from complex environment,and the heading angle of inertial navigation data is easily divergent in scenario of mobile phone vehicle positioning.To address these problems,this paper proposes an RTK/DR loose combination positioning method combined with OSM map data.In the process of dead reckoning,based on the OSM data,combined with the information of combined positioning results and vehicle motion state,a geometric matching method from point to line was designed,and the matched road direction was used to correct heading angle.In the loose combination stage,the standard Kalman filter was used to estimate the position and velocity.In order to reduce the influence of large drift or jump of RTK on the results of loose combination,a loose combination switch was set,which can comprehensively judge whether to update the measurement by combining the covariance matrix,the vehicle's moving direction and the change of RTK positioning heading angle in RTK robust Kalman solution.Then six groups of experiment were carried out by using P30 and P40 smart phones.The results show that the introduction of OSM data can effectively solve the accumulation of heading angle error,which makes dead reckoning trajectory more consistent with the benchmark.Compared with mobile RTK,the proposed RTK/DR loose combination with switch improves positioning performance,and effectively suppresses error points of large jumps.