The invention provides a deployment optimal mode research method for an uncompartmentalized oilfield fluvial facies reservoir horizontal well. The method comprises the following steps: step 1, according to sedimentary characteristics of a fluvial facies reservoir, respectively establishing a fine 3D geological model of a braided reservoir and a meandering stream reservoir; step 2, establishing a numerical simulation model of the braided reservoir and a meandering stream reservoir, according to the established numerical simulation model, determining a remaining oil distribution mode; step 3, determining a horizontal well mining economic limit; step 4, designing configuration methods of the horizontal well and a well pattern, and setting injection-production parameters; step 5, developing scheme design and scheme optimization, and determining horizontal well deployment modes in different well patterns in different sedimentary reservoirs. The deployment optimal mode research method for an uncompartmentalized oilfield fluvial facies reservoir horizontal well is good in pertinency, and has very good practicality. The method can effectively improve unit recovery efficiency of an uncompartmentalized oilfield thick oil pay, and greatly increase cumulative oil production of a maturing field.