A new Microfluidic continuous flow analysis sensor is established for the determination of soluble silicate in seawater based on the reaction of silicate with ammonium molybdate to form a yellow silicomolybdate complex, and further reduction to silicomoIybdenum blue by ascorbic acid. Theanalyzing cycle of the sensor is about 300 s, Double optical absorbance path method is adopted in this sensor to expand the measuring range, and the linear range of the sensor reaches 0～400 mol·L-1 with limit of detection of each absorbance cell were 45.1 nmol·L-1 and 1.6 μmol·L-1 respectively. There are no evident effects on the performance of determination of this sensor when samples’ salinity is above 15, and the actual water the recovery rate is between 98.1%～104.0%. In November 2015, this sensor was deployed in a research vessel for a sea trail in Jiaozhou Bay involving 20 sites, the data acquired from the sensor were compared with those from sampling then by lab analyzing. The results obtained in situ coincide with those from lab analyzing, and indicating This sensor has the advantages of high accuracy, simple and high integration, water consumption, and strong anti-interference ability, and suitable for in situ silicate monitoring.