There exists a tradeoff between the mechanical resonant frequency (fm) and the mechanical quality factor (Qm) of a nanomechanical transducer, which resulted in a tradeoff between the band width and sensitivity. Here, we present monolithic silicon nitride (Si3N4) cavity optomechanical transducer, in which high fm and Qm are achieved simultaneously. A nanoscale tuning fork mechanical resonator is near-field coupled with a microdisk optical resonator, allowing the displacement of mechanical resonator to be optically read out. Compared with a single beam with same length, width, and thickness, the tuning fork simultaneously increases fm and Qm by up to 1.4 and 12 times, respectively. A design enabled, on-chip stress tuning method is also demonstrated. By engineering the clamp design, we increased the stress in the tuning fork by 3 times that of the Si3N4 film. A fundamental mechanical in-plane squeezing mode with fm ≈ 29 MHz and Qm ≈ 2.2×105 is experimentally achieved in a high-stress tuning fork device, corresponding to a fmQm product of 6.35×1012 Hz. The tuning fork cavity optomechanical sensors may find applications where both temporal resolution and sensitivity are important such as atomic force microscopy.