The invention discloses a splice welding device for a vehicle frame used for engineering machinery and a splice welding method for the vehicle frame. The splice welding device comprises a splice point production line and a welding production line which are both divided into a plurality of work positions respectively. The splice point production line comprises a transfer vehicle and a circulating type line body which are connected. The welding production line comprises a reciprocating type line body, an upender, transfer trolleys and a lifting platform. The transfer trolleys are connected with the reciprocating type line body. The welding production line is arranged on the side in the advancing direction of the circulating type line body of the splice point production line. The splice point production line is connoted with the welding production line through a transition device. The transfer trolleys all run on the ground. The whole production line foundation is simple, and not a large amount of rectification needs to be conducted on the foundation, so that investment is less. The work positions are divided for splice welding of the vehicle frame, and a climbing device, a vehicle frame overturn device, a lifting device and other devices which are matched with the work positions are designed, so that linearization production of vehicle frame splice welding is achieved, and the quality problems of missing splice and missing welding in the splice welding process are solved.