Under conventional approach currently practiced in elementary schools, some subjects are delivered in both partial and integrated model. Partial model is addressed to strengthen student understanding concerning the structure of subject matters. while integrated model is adressed to stengthen the student understanding concerning in the connection among related subject matters. This model will create deep understanding upon concept learnt by each student. This study aimed to identify the impact of thematic approach (application) on teaching mathematic in elementary school. Using a case study, it was conducted in SDN 69 and SDN 70 kandang limun, bengkulu during 2006/2007 academic year.Research subject were student of grad 3. Result showed that there was a significant difference in mathematic achievement between thematic and conventional teaching treatment. The t-test revealed that thematic approach reached higher (79,091) value compared to conventional approach (54,615).Another result revealed that during experimenting thematic approach, students started as enjoy learning mathematic (73%) and claimed ada get many experiences and knowledges from thematic approach during teaching time. It is recommended that teacher of Grade 1,2 and 3 should apply thematic approach while teaching Mathematics.