In the present work, the design of a micromachined thermal accelerometer based on convection effect was studied. The accelerometer sensitivity and especially the frequency response have been experimentally and numerically studied with low cavity volume. Although this type of sensor has already been intensively examined, few information concerning the frequency response modeling is currently available. In particular, no experimental result about frequency response for low volume and their variation according to the external temperature variation was reported in the literature. In certain particular condition, we assumed that a bandwidth of 120Hz at −3dB has been measured. By using numerical resolution of fluid dynamics equations with the computational fluid dynamics (CFD) software package Fluent V6.2 and a simple model based on thermo-conduction, a good accordance with the experimental results has been demonstrated. So, the effects of these two parameters like the volume and the external temperature variation on the thermal accelerometer response have been theoretically, experimentally and numerically investigated.