The flow velocity was measured using homemade Marriott device under different conditions，which certified that the Marriott device could provide a constant velocity and investigate the factors to influence its constant velocity feature．The water pipes were assembled by two types connecting to the Marriott device．The pressure，flow velocity and height difference of water at different positions in the pipes were measured to verify Bernoulli’s theorem experimentally．Meanwhile，Bernoulli constant( C) of the main flow pipe was equal to the sum of the tributary pipes by measuring parameters in main and tributary pipes the main，which extended the

application Bernoulli’s theorem in the field of tributary pipes．