How to transmit packet size grater then 64 Bytes through cc2500 chip?
In order to transmit more than 64 bytes, you basically have to fill up the FIFO with the first 64 byte chunk, then check for the TX FIFO emptying. Place the radio in TX mode and as its transmitting, the TX FIFO gets emptied as bytes are sent. Once it reaches a threshold(watermark), you fill up the rest of the FIFO with more packet bytes.

In order to detect the FIFO threashold, you have to configure the device correctly to send large packets as well as the watermark and then either:

1) Poll the device to see the number of bytes in the TX FIFO
2) Configure one of the GDO interrupts to trigger when watermark is reached.

Take a look at this and App Note AN049, which should have an example of how to do this.